Wiring substrate, semiconductor device and manufacturing method thereof

ABSTRACT

The present invention provides a method for forming a wiring having a minute shape on a large substrate with a small number of steps, and further a wiring substrate formed by the method. Moreover, the present invention provides a semiconductor device in which cost reduction and throughput improvement are possible due to the small number of steps and reduction of materials and which has a semiconductor element with a minute structure, and further a manufacturing method thereof. According to the present invention, a composition including metal particles and organic resin is irradiated with laser light and a part of the metal particles is baked to form a conductive layer typified by a wiring, an electrode or the like over a substrate. Further, a semiconductor device having the baked conductive layer as a wiring or an electrode is formed.

This application is a divisional of application Ser. No. 11/151,003filed on Jun. 13, 2005 now U.S. Pat. No. 7,494,923.

BACKGROUND OF THE PRESENT INVENTION

1. Field of the Present Invention

The present invention relates to a wiring substrate and a semiconductordevice having a semiconductor element formed by a droplet dischargingmethod typified by an inkjet method, and further manufacturing methodsthereof.

2. Description of the Related Art

Conventionally, an active matrix driving type display panel orsemiconductor integrated circuit including a semiconductor elementtypified by a thin film transistor (hereinafter, TFT) or a MOStransistor is formed by patterning each thin film with light-exposureprocess (hereinafter, a photolithography process) using a photomask.

In the photolithography process, resist is applied to a whole substrate,pre-baked, then the substrate is irradiated with ultraviolet rays or thelike using a photomask and a resist pattern is formed by development.After that, a thin film existing outside a portion to be a film patternor a wiring (a film of a semiconductor material, an insulator material,or a conductor material) is etch-removed with the resist pattern as amask pattern for forming a film-pattern or a wiring.

Reference 1 (Japanese Patent Laid-Open No. 2000-188251) describes atechnique for forming a film on a semiconductor wafer with an apparatusthat can continuously discharge resist from its nozzle to have a linearshape with a small diameter so as to reduce loss of materials forforming films.

However, when forming a wiring or a film-pattern using a conventionalphotolithography process, almost all materials of the wiring or the filmpattern and a resist material become wasted and the number of steps offorming the wiring or a mask pattern becomes large; therefore throughputis decreased.

A light-exposure apparatus used in the photolithography process hasdifficulty in exposing a large substrate to light at once. Accordingly,a manufacturing method of a semiconductor device using a large substrateneeds a plurality of times of light-exposure, which leads tomisalignment with an adjacent pattern and reduction in yield.

It is necessary to discharge a material solution whose droplet diameteris small in order to form a semiconductor element that is minute andoccupies a small area by a droplet-discharging method. Reduction indiameter of the discharge opening is required to be small so as todischarge such a material solution. However, in this case, the tip ofthe discharge opening is clogged with the material solution because acomposition of the material solution is attached thereto, dried orsolidified therein, and thus it is difficult to discharge a constantamount of material solution continuously or stably. Consequently, thereis a problem in that throughput or yield of a semiconductor device usingthe semiconductor element is reduced.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above describedproblems. It is an object of the present invention to provide a methodfor forming a wiring on a large substrate with a small number of steps,and further a wiring substrate formed by the method.

Moreover, it is another object of the present invention to provide asemiconductor device in which cost reduction and throughput improvementare possible due to the small number of steps and reduction of materialsand which has a semiconductor element with a minute structure, andfurther a manufacturing method thereof.

According to the present invention, a composition including metalparticles and organic resin that has been formed over a substrate isirradiated with laser light and a part of the metal particles is bakedto form the substrate having a conductive layer typified by a wiring, anelectrode or the like.

According to the present invention, a semiconductor device having thebaked conductive layer as a wiring or an electrode is formed.

The composition is one in which metal particles are dispersed ordissolved in one or a plurality of organic resin to serve as a binder, asolvent, a dispersant or a coating agent. Accordingly, a portion of theorganic resin evaporates and meal particles are baked and adhered toeach other by laser irradiation onto the composition to form aconductive layer. At the time, the composition remains on one side oropposite sides of the conductive layer.

The width of a beam spot of laser light is adjusted appropriately,thereby forming a conductive layer having a desired width. Accordingly,a conductive layer having a narrower width (typically, 10 μm or less,preferably 0.3 to 1 μm, more preferably 0.5 to 0.8 μm) can be formed byemitting laser light having a beam-spot width narrower than a width ofthe composition with a laser beam directly-drawing apparatus or thelike. A semiconductor element having a short channel structure can beformed using such a conductive layer as a gate electrode, and asemiconductor device that operates at high speed and in which elementsare integrated with high density can be manufactured.

As the composition remaining on one side or opposite sides of theconductive layer, metal particles are dispersed in organic resin servingas a solvent. Accordingly, the composition is conductive or insulativedepending on the density of metal particles. In other words, thecomposition provided on a side of the conductive layer is conductivewhen the density of metal particles is high and the contact area ofparticles is large. On the other hand, when the density of metalparticles is low and the periphery of metal particles is coated withorganic resin, the composition remaining on one side or opposite sidesof the conductive layer is insulative. Thus, when the compositionremaining on one side or opposite sides of the conductive layer isinsulative, only the conductive layer irradiated with laser light servesas a wiring or an electrode. Therefore, a stable conductive layer thatis resistant to falling down can be formed even when the conductivelayer whose aspect ratio is large (longitudinal length>lateral length)is adopted. The coverage of an insulating layer or a semiconductor layerto be formed later can be improved and thus, a highly reliablesemiconductor element can be formed.

The present invention has the following structures.

One of the present invention is a wiring substrate including: a wiringformed over a substrate, which is a conductive layer in which firstmetal particles are baked; and an organic resin layer which is providedon a side of the wiring and in which second metal particles aredispersed, wherein the first metal particles and the second metalparticles are formed from the same metal element. In this case, themetal element may include a plurality of metal elements.

One feature of the present invention is a wiring substrate including awiring and an organic resin layer provided on the sideface thereof,wherein the organic resin layer includes metal particles and the wiringincludes the metal particles that are baked. In addition, a conductivelayer, an insulating layer or a semiconductor layer to be in contactwith the wiring or the organic resin layer may be provided. Note thatthe organic resin layer is provided only on the opposite sides or oneside of the wiring. At this time, the wiring is linear.

The rate of the metal element in the wiring is higher than that in theorganic resin layer.

Further, the rate of organic resin in the wiring is lower than that inthe organic resin layer.

The cross section of the wiring is a quadrilateral having approximateorthogonal angles or an approximate trapezoid. In the case of thetrapezoid-shaped cross section, the width of a wiring contacting with asubstrate may be narrower than that of the width of the wiring surface.Alternatively, the width of the wiring contacting with the substrate maybe wider than that of the width of the wiring surface.

The width of the wiring is 0.3 μm or more and 1.0 μm or less, preferably0.5 μm or more and 0.8 μm or less.

One feature of the present invention is a method for manufacturing awiring substrate, including the steps of: forming a pattern bydischarging a composition containing a metal particle and an organicresin over a substrate; and irradiating the pattern with laser light tobake a portion of the metal particle included in the pattern to form awiring. In this case, irradiation of the laser light is preferablyconducted in a direction parallel to a major axis of the pattern. Thelaser light is continuous wave laser light or pulsed oscillation laserlight.

One feature of the present invention is a semiconductor device includinga semiconductor element having the wiring as a gate electrode. As thesemiconductor element, for example, a TFT, a field effect transistor(FET), a MOS transistor, a bipolar transistor, an organic semiconductortransistor, an MIM element, a memory element, a diode, a photoelectricconverter, a capacitor, a resistor and the like can be used. The TFT is,for example, a staggered TFT, an inverted staggered TFT (a channel-etchtype TFT or a channel protective type TFT), a top gate coplanar TFT, abottom gate coplanar TFT and the like.

One feature of the present invention is a method for manufacturing asemiconductor device, including the steps of: forming a pattern bydischarging a composition containing a metal particle and an organicresin over a substrate; irradiating the pattern with laser light to bakea portion of the metal particle included in the pattern to form a gateelectrode; and forming a thin film over a region of the gate electrodeand the pattern that is not irradiated with the laser light.

In the present invention, the semiconductor device is, for example, anintegrated circuit, a display device, a wireless tag, an IC tag, and thelike that each include a semiconductor element. The display device is,for example, a liquid crystal display device, a light emitting displaydevice, a DMD (Digital Micromirror Device), a PDP (Plasma DisplayPanel), an FED (Field Emission Display), an electrophoresis displaydevice (electronic paper) and the like.

In the present invention, a display device means a device using adisplay element, that is, an image-displaying device. Further, a modulein which a connector such as a flexible printed circuit (FPC) or a TAB(Tape Automated Bonding) tape or a TCP (Tape Carrier Package) areattached to a display panel, a module in which a printed wiring board isprovided for an edge of a TAB tape or a TCP, a module in which an IC(Integrated Circuit) and a CPU are directly mounted on a display elementby a COG (Chip On Glass) method are all included in the display device.

According to the present invention, a portion of a composition includingmetal particles and organic resin is directly irradiated with a laserbeam to bake the metal particles, thereby forming a wiring having aminute and narrow width without using a photo mask. In addition, thewidth of the laser beam is made narrow and a part of the composition isirradiated with the laser beam; therefore, micro fabrication of afilm-pattern formed by a droplet-discharging method is possible and asemiconductor element having a minute structure can be formed. Moreover,a semiconductor element having a short channel length can be formed byusing the conductive layer as a gate electrode. Therefore, asemiconductor device in which a semiconductor element that operates athigh speed is integrated with high density can be formed.

The metal particles contained in the composition dropped by a dropletdischarging method are baked without being heat-treated using a furnaceor the like, thereby forming the conductor layer. Therefore, it ispossible to manufacture a wiring substrate or a semiconductor deviceusing a plastic substrate that has inferior heat-resistance and aflexible substrate. Accordingly, it is possible to manufacture a lightand thin semiconductor device and further a liquid crystal televisionand an EL television having the semiconductor device.

When a droplet discharging method is employed in forming a film pattern,a droplet can be discharged onto an arbitrary position by changing arelative position of a nozzle that is a discharge opening of a dropletincluding its film material and a substrate. In addition, a thicknessand a width of a pattern to be formed can be adjusted depending on anozzle diameter, the amount of droplets to be discharged, and a relativerelationship between movement speed of a nozzle and that of a substrateto be provided with a discharged droplet. Accordingly, a film patterncan be formed in a desired portion with high accuracy by dischargingeven over a large substrate having a side of 1 m to 2 m or more. Yieldcan be improved because misalignment with an adjacent film pattern isnot caused. As a result, a semiconductor device can be manufactured withthe small number of steps and with high yield.

Moreover, a liquid crystal television and an EL television having asemiconductor device that is formed according to the above describedmanufacturing steps can be manufactured at low cost with high throughputand yield.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1D are each a perspective view showing a manufacturing stepof a wiring according to the present invention;

FIG. 2 is a top view showing a manufacturing step of a wiring accordingto the present invention;

FIGS. 3A to 3C are each a cross-sectional view showing a wiringaccording to the present invention;

FIGS. 4A to 4F are each a cross-sectional view showing a manufacturingstep of a semiconductor device according to the present invention;

FIGS. 5A to 5F are each a cross-sectional view showing a manufacturingstep of a semiconductor device according to the present invention;

FIGS. 6A to 6F are each a cross-sectional view showing a manufacturingstep of a semiconductor device according to the present invention;

FIGS. 7A to 7E are each a cross-sectional view showing a manufacturingstep of a semiconductor device according to the present invention;

FIGS. 8A to 8D are each a cross-sectional view showing a manufacturingstep of a semiconductor device according to the present invention;

FIGS. 9A to 9E are each a cross-sectional view showing a manufacturingstep of a semiconductor device according to the present invention;

FIG. 10 shows a droplet discharging apparatus that can be applied to thepresent invention;

FIG. 11 shows a laser beam directly-drawing apparatus that can beapplied to the present invention;

FIGS. 12A to 12C are each a cross-sectional view showing a manufacturingstep of a semiconductor device according to the present invention;

FIGS. 13A to 13C are each a cross-sectional view showing a manufacturingstep of a semiconductor device according to the present invention;

FIGS. 14A to 14C are each a cross-sectional view showing a manufacturingstep of a semiconductor device according to the present invention;

FIGS. 15A and 15B are each a cross-sectional view showing amanufacturing step of a semiconductor device according to the presentinvention;

FIG. 16 is a top view showing a manufacturing step of a semiconductordevice according to the present invention;

FIGS. 17A and 17B each show a method for dropping a liquid crystal thatcan be applied to the present invention;

FIG. 18 shows a structure of a liquid crystal display module accordingto the present invention;

FIGS. 19A and 19B are each a cross-sectional view showing amanufacturing step of a semiconductor device according to the presentinvention;

FIGS. 20A and 20B are each a cross-sectional view showing amanufacturing step of a semiconductor device according to the presentinvention;

FIGS. 21A and 21B are each a cross-sectional view showing amanufacturing step of a semiconductor device according to the presentinvention;

FIG. 22 is a top view showing a manufacturing step of a semiconductordevice according to the present invention;

FIGS. 23A to 23F each show a mode of a light-emitting element that canbe applied to the present invention;

FIGS. 24A to 24F each show an equivalent circuit of a light-emittingelement that can be applied to the present invention;

FIGS. 25A and 25B each show a structure of a light-emitting displaypanel according to the present invention;

FIGS. 26A to 26C are each a top view showing a mounting method of adriver circuit in a display device according to the present invention;

FIG. 27 is a block diagram showing an example of an electronic device;

FIG. 28 shows an example of an electronic device;

FIGS. 29A and 29B each show an example of an electronic device;

FIG. 30 shows contact angles in a low-wettability region and ahigh-wettability region;

FIG. 31 is a cross-sectional view showing a wiring according the presentinvention; and

FIGS. 32A and 32B each a view for explaining a resistance value of awiring according to the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Embodiment Modes according to the present invention will hereinafter bedescribed with reference to the accompanying drawings. The presentinvention can be carried out in many different modes, and it is easilyunderstood by those skilled in the art that modes and details hereindisclosed can be modified in various ways without departing from thespirit and the scope of the present invention. It should be noted thatthe present invention should not be interpreted as being limited to thedescription of the embodiment modes to be given below. Note that thesame reference numerals are used for the same portions through alldrawings and detailed description is omitted.

Embodiment Mode 1

In Embodiment Mode 1, a process for forming a wiring having a thin widthby irradiation of a laser beam (hereinafter referred to as laser light)is described with reference to FIGS. 1A to 1D, 2 and 3A to 3C.

FIG. 2 is a top view of a substrate 101 in which pixels are arranged inmatrix. On the substrate 101, a second conductive layer 113 serving as agate wiring of a semiconductor element that is to be formed later and afirst conductive layer 105 serving as a gate electrode to be connectedthereto are shown by a solid line. Note that a dashed line shows asource wiring, a semiconductor region, a source electrode, a drainelectrode, a pixel electrode and the like of the semiconductor elementthat is to be formed later.

FIGS. 1A to 1D are each a perspective view of a cross-section takenalong A-B in FIG. 2. As shown in FIG. 1A, a first pattern material isdischarged on the substrate 101 by a droplet discharging method anddried to form a first pattern 102. Note that the droplet dischargingmethod is a method by which a pattern having a desired shape is formedby discharging droplets of an adjusted composition from a minuteopening.

A glass substrate, a quartz, substrate, a ceramic substrate such asalumina, a plastic substrate, a silicon wafer, a metal plate and thelike can be used as the substrate 101. In the case of a glass substrateas the substrate 101, a glass substrate having a large area can beemployed, e.g., 320 mm×400 mm, 370 mm×470 mm, 550 mm×650 mm, 600 mm×720mm, 680 mm×880 mm, 1000 mm×1200 mm, 1100 mm×1250 mm, 1150 mm×1300 mm.

As representative examples of the plastic substrate, a plastic substrateformed from PET (polyethylene terephthalate), PEN (polyethylenenaphthalate), PES (polyether sulfide), polypropylene, polypropylenesulfide, polycarbonate, polyetherimide, polyphenylene sulfide,polyphenylene oxide, polysulfone, or polyphthalamide, or a substrateincluding an organic material dispersed with inorganic particles ofseveral nanometers in diameter, or the like can be given. In addition, asurface of the substrate is not required to be flat, and may be unevenor have a curved surface.

A conductor (a metal particle) dissolved or dispersed in organic resinis used as a composition to be discharged from a discharge opening as amaterial of the first pattern. A particle of a metal such as Ag, Au, Cu,Ni, Pt, Pd, Ir, Rh, W, Al, Ta, Mo, Cd, Zn, Fe, Ti, Si, Ge, Zr, or Ba, aminute particle of silver halide, or a dispersant nanoparticle thereof,can be used as the metal particle. Alternatively, a conductive oxidematerial such as ITO (indium tin oxide), ITO containing silicon oxide,organic indium, organic tin, or zinc oxide (ZnO), which is typicallyused as a transparent conductive film or the like, can be used. Inaddition, the first pattern 102 can be formed by stacking conductivelayers made of such materials. One or a plurality of organic resinselected from organic resin that can serve as a binder of metalparticles, a solvent, a dispersing agent, and a coating agent can beused as the organic resin. Typically, polyimide, acrylic, novolac resin,melamine resin, phenol resin, epoxy resin, silicone resin, furan resin,diallyl phthalate resin, or a known organic resin can be used.

The viscosity of the composition is preferably in the range of 5 mPa·sto 20 mPa·s so that a metal particle can be smoothly discharged from adischarge opening. The surface tension is preferably 40 mN/m. Note thatthe viscosity of the composition and the like may be appropriatelyadjusted in accordance with a solvent to be used and intended use. Forexample, the viscosity of a composition in which ITO, indium tin oxidecontaining silicon oxide, organic indium, organic tin, or the like isdissolved or dispersed in organic resin is 5 mPa·s to 20 mPa·s, theviscosity of a composition in which silver is dissolved or dispersed inorganic resin is 5 mPa·s to 20 mPa·s, and the viscosity of a compositionin which gold is dissolved or dispersed in organic resin is 10 mPa·s to20 mPa·s.

The content of a conductor in a composition is 30 to 70 wt %, preferably40 to 60 wt %. The content of a conductor in the first pattern is higherthan that the content of a conductor in the composition so that thesolvent of the composition is dried to form the first pattern.

The diameter of the metal particle is preferably made as small aspossible for the purpose of preventing a clogged nozzle and formanufacturing a highly-minute pattern, although it depends on thediameter of each nozzle, a desired shape of a pattern, and the like.Preferably, the diameter is preferably 0.1 μm or less. The metalparticle is formed by a known method such as an electrolyzing method, anatomizing method or a wet reduction method and the particle size thereofis typically approximately 0.5 μm to 10 μm. However, when a gasevaporation method is employed, a nanoparticle protected by a dispersantis minute, approximately 7 nm. When each surface of nanoparticles iscovered with a coating agent, the nanoparticles do not cohere in thesolvent and are uniformly dispersed in the solvent at room temperature,and show a property similar to that of liquid.

The step of discharging the composition may be performed under lowpressure. This may be conducted because the organic resin of thecomposition is evaporated during a period from discharging of acomposition till landing of the composition on an object to be treated,and the energy density of the laser light can be decreased in a bakingstep of metal particles.

Then, the first pattern 102 is irradiated with laser light 103 with alaser beam directly-drawing apparatus. Here, the laser light is moved inthe direction shown by an arrow 104. By this step, the organic resin ofthe composition in a region that is irradiated with laser light isvaporized to be removed. In addition, fusion between metal particlesproceeds by energy of the laser light to form a first conductive layer105 as shown in FIG. 1B.

The first pattern is irradiated with laser light, so that organic resinin the first pattern is vaporized to be removed. At this time, thecontent of a conductor in the first conductive layer 105 is higher thanthat of the first pattern.

When the metal particles are constituted by plural metal elements, thefirst conductive layer has the same composition as the metal particles.Note that the first conductive layer can be an alloy having acomposition different from the metal particles when the energy of thelaser light is high. However, in this case, the metal elements containedin the first conductive layer are the same as the metal particles.

A region that is not irradiated with the laser light 103 remains as thefirst pattern. The first pattern remaining on the opposite sides of thefirst conductive layer is referred to as a first organic resin layer106. In addition, the first organic resin layer 106 is provided on theopposite sides of the first conductive layer. However, the presentinvention is not limited thereto and the first organic resin layer 106may be provided on only one side of the first conductive layer. Thefirst organic resin layer is conductive or insulative depending on arate of dispersed metal particles. The atmosphere during laserirradiation is an oxygen atmosphere, a nitrogen atmosphere oratmospheric air. However, it is preferable that laser irradiation beconducted under the oxygen atmosphere in which organic resin dissolvingor dispersing metal particles is easily removed.

Here, a laser beam directly-drawing apparatus is described withreference to FIG. 11. As shown in FIG. 11, the laser beamdirectly-drawing apparatus 1001 includes: a personal computer(hereinafter referred to as a PC) 1002 for conducting various types ofcontrol in emitting a laser beam; a laser oscillator 1003 for outputtingthe laser beam; a power source 1004 of the laser oscillator 1003; anoptical system (ND filter) 1005 for attenuating the laser beam; anacousto-optic modulator (AOM) 1006 for modulating intensity of the laserbeam; an optical system 1007 having a lens for enlarging or reducing thesize of a cross section of the laser beam, a mirror for changing a lightpath, and the like; a substrate movement mechanism 1009 having an Xstage and a Y stage; a D/A converter 1010 for analog-digital convertingcontrol data outputted from the PC; a driver 1011 for controlling theacousto-optic modulator 1006 in accordance with an analog voltageoutputted from the D/A converter; and a driver 1012 for outputting adriving signal for driving the substrate movement mechanism 1009.

A laser oscillator that can oscillate ultraviolet light, visible light,or infrared light can be used as the laser oscillator 1003. An excimerlaser of ArF, KrF, XeCl, Xe, or the like, a gas laser of He, He—Cd, Ar,He—Ne, BF, or the like, a solid laser using a crystal such as YAG, YVO₄,YLF, or YAlO₃ doped with Cr, Nd, Er, Ho, Ce, Co, Ti, or Tm, asemiconductor laser of GaN, GaAs, GaAlAs, InGaAsP, or the like can beused as the laser oscillator. Note that it is preferable to apply any ofsecond to fifth harmonics of a fundamental wave to the solid laser.

Subsequently, an irradiation method with the use of the laser beamdirectly-drawing apparatus is described. When a substrate 1008 is set onthe substrate movement mechanism 1009, the PC 1002 detects a position ofa marker marked on the substrate with a camera which is not shown inFIG. 11. Next, the PC 1002 generates movement data for moving thesubstrate movement mechanism 1009 based on position data of the detectedmarker and data for drawing a pattern that has been inputted in advance.Thereafter, the PC 1002 controls the amount of output light from theacousto-optic modulator 1006 through the driver 1011. Accordingly, afterthe laser beam outputted from the laser oscillator 1003 is attenuated bythe optical system 1005, the amount of the laser beam is controlled bythe acousto-optic modulator 1006 to be the predetermined amount. On theother hand, a light path and a beam spot shape of the laser beamoutputted from the acousto-optic modulator 1006 is changed by theoptical system 1007 and the laser beam is condensed by a lens.Thereafter, a composition (the first pattern) formed over the substrateis irradiated with the laser beam to bake metal particles in thecomposition. At this time, movement of the substrate movement mechanism1009 in an X direction and a Y direction is controlled in accordancewith the movement data generated by the PC 1002. Consequently, apredetermined position is irradiated with the laser beam, and the metalparticles in the composition are baked.

Here, the laser beam is emitted moving the laser beam in X-Y axisdirection. In this case, a polygon mirror or a galvano mirror ispreferably used as the optical system 1007.

A composition containing Ag (hereinafter, Ag paste) is selectivelydischarged and a part of the Ag paste is irradiated with a laser beamdescribed above to appropriately bake the Ag particles, and thus thefirst conductive layer 105 is formed to have a thickness of 600 to 800nm. Here, the region that is irradiated with the laser beam becomes thefirst conductive layer. Thus, the width of the first conductive layerbecomes almost equal to the width of a beam spot when a laser beam isscanned once. A laser beam with lower wavelength is preferably emittedin order to form the first conductive layer having more minute width. Inthis embodiment mode, laser light having any wavelength of ultravioletlight to infrared light is used. Consequently, the width of the beamspot can be made thin. The first conductive layer 105 serves as a gateelectrode. Therefore, the first pattern 102 is irradiated with the laserlight 103 having thinner beam-spot width, and thus a semiconductorelement having a short channel structure can be formed. The width of thefirst conductive layer is 0.3 to 1 μm, preferably 0.5 to 0.8 μm.Consequently, a semiconductor element having a short channel structurecan be formed. In addition, the organic resin layer 106 in which metalparticles are dispersed is formed on the opposite sides of the firstconductive layer 105.

This embodiment mode shows one example of forming the conductive layerby emitting laser light on the first pattern. However, a semiconductorlayer or an insulating layer can be formed appropriately instead of theconductive layer. In this case, a semiconductor material or aninsulating material may be used appropriately for the first pattern.

Next, as shown in FIG. 1C, the first pattern 102 is irradiated withlaser light 111 so as to overlap a part of the first conductive layer105. Here, the laser light 111 is moved in the direction shown by anarrow 112. It is preferable to emit the laser light 111 having widerbeam width than that of the laser light 103 so as to form a gate wiring.Consequently, as shown in FIG. 1D, a second conductive layer 113 isformed. The second conductive layer 113 is a conductive layer in whichmetal particles are baked and a second organic resin layer 114 in whichmetal particles are dispersed is formed on the opposite sides of thesecond conductive layer 113. Note that the second organic resin layermay be formed on only one side of the second conductive layer.

FIG. 2 is a top view of the substrate at this stage. The first organicresin layer 106 dispersed with metal particles is formed on the oppositesides of the first conductive layer 105 to serve as a gate electrode.The second organic resin layer 114 dispersed with metal particles isformed on the opposite sides of the second conductive layer 113 to serveas a gate wiring. Further, the first conductive layer 105 is connectedto the second conductive layer 113.

The cross-sectional shape of the first conductive layer 105 is describedwith reference to FIGS. 3A to 3C.

FIG. 3A is an enlarged view of a cross-section of the first conductivelayer 105, which is a perpendicular to the scanning direction of laserlight (the arrow 104 in FIG. 1A). An organic resin layer 106 a dispersedwith metal particles is formed on the opposite sides of a firstconductive layer 105 a. The cross-sectional shape of the firstconductive layer 105 a is a quadrilateral having approximate orthogonalangles. In other words, the width of a top surface of the firstconductive layer is substantially equal to the width of the surface thatis in contact with the substrate.

FIG. 3B is an enlarged view of a cross-section similarly to FIG. 3A. Anorganic resin layer 106 b dispersed with metal particles is formed onthe opposite sides of a first conductive layer 105 b. The cross-sectionshape of the first conductive layer 105 b is substantially a trapezoidshape. In other words, the width of the surface that is in contact withthe substrate is narrower than the width of a top surface of the firstconductive layer. This shape can be obtained when the energy intensityof the laser beam has a Gaussian shape and the energy distribution ofthe laser beam to the substrate is convex.

FIG. 3C is an enlarged view of a cross-section similarly to FIG. 3A. Anorganic resin layer 106 c dispersed with metal particles is formed onthe opposite sides of a first conductive layer 105 c. Thecross-sectional shape of the first conductive layer 105 c issubstantially a trapezoid shape. In other words, the width of thesurface of the first conductive layer that is in contact with thesubstrate is wider than the width of a surface of the first conductivelayer. This shape can be obtained when the energy of the emitted laserlight is conducted in the horizontal direction (a direction along asubstrate surface) and the width of the conductive layer on thesubstrate 101 side becomes wide.

In FIGS. 3A to 3C, the conductive layers 105 a to 105 c are formed to bein contact with the substrate surface. However, an organic resin layerdispersed with metal particles may be formed between the firstconductive layer and the substrate 101 without being limited to thisstructure.

Then, FIG. 31 shows a mode of baked metal particles and dispersed metalparticles in FIG. 3A. In the first conductive layer 105 a irradiatedwith laser light, large metal particles 151, in which plural metalparticles are baked, cohere. Accordingly, the rate of organic resin inthe first conductive layer is small. On the other hand, in the organicresin layer 106 a dispersed with metal particles, a large number ofmetal particles 153 are dispersed in the organic resin 152. Thus, therate of organic resin in the organic resin layer is higher than that inthe first conductive layer.

A wiring having a film pattern with a thin width can be formed throughthe above described steps.

Embodiment Mode 2

Embodiment Mode 2 describes a manufacturing method of a semiconductorelement with reference to FIGS. 4A to 4F. In this embodiment mode, achannel etch type TFT of a bottom gate TFT as a semiconductor element isdescribed.

As shown in FIG. 4A, a first pattern 202 is formed on a substrate 201 bya droplet discharging method. The material of the first pattern 102shown in Embodiment Mode 1 can be used appropriately for the material ofthe first pattern 202.

In this embodiment mode, the first pattern 202 is formed by selectivelydischarging Ag paste dispersed with silver particles of several nm.

Then, a part of the first pattern 202 is irradiated with laser light 203using a laser beam directly-drawing apparatus to form a first conductivelayer 211 as shown in FIG. 4B. At this time, in a region that is notirradiated with the laser light 203, the Ag paste remains. Hereinafter,the region where the Ag paste remains is shown as an organic resin layer212 dispersed with metal particles. Fine particles that are conductiveoverlap one another irregularity three dimensionally, and thus the firstconductive layer 211 is formed. In other words, the first conductivelayer 211 is constituted by three dimensional aggregate particles.Accordingly, the surface has slight unevenness. In addition, fineparticles melt depending on a heating temperature and heating time ofthe Ag paste and an aggregate of fine particles can be obtained. Sincethe size of this aggregate increases depending on the heatingtemperature and the heating time of the Ag paste, the conductive layerhas varying heights of elevation on the surface. Note that the region inwhich fine particles are melted become polycrystalline in some cases.The width of the first conductive layer 211 depends on a diameter of alaser beam. Therefore, the first conductive layer having narrow widthcan be formed by irradiating the first pattern with laser light havingsmall beam diameter. A TFT having a short channel structure can beformed because the first conductive layer serves as a gate electrode.

At this time, the first pattern is irradiated with a plurality of laserlight so as not overlap one another, so that a multigate electrode canbe formed. Accordingly, a TFT having a multi gate structure can beformed later. At this time, the plurality of laser light is preferablyemitted to be parallel with one another.

Next, as shown in FIG. 4C, a first insulating layer 221 serving as agate insulting film, a first semiconductor film 222 and a secondsemiconductor film 223 that is conductive are formed over the firstconductive layer 211 and the organic resin layer 212 dispersed withmetal particles. Here, the first insulating layer 221 and films to beformed after the first insulating layer 221 are preferably formed at atemperature lower than the temperature at which organic resin containedin a composition that is a material of the first pattern 202 reacts. Ifthe first insulating layer 221 and the films to be formed after thefirst insulating layer 221 are formed at a temperature higher than thatthe reaction temperature of the organic resin, the organic resin reactsto discharge a gas. The films are peeled by this gas and thus, the yieldof a semiconductor element and a semiconductor device having thesemiconductor element are reduced. Therefore, the yield can be enhancedby forming the films at a temperature lower than the reactiontemperature of organic resin.

The first insulating layer 221 is formed as a single layer or a stackedlayer of silicon nitride, silicon oxide or other insulating filmscontaining silicon by a thin-film forming method such as a plasma CVDmethod or a sputtering method. In addition, the first insulating layerpreferably has a stacked structure in which a silicon nitride film(silicon nitride oxide film), a silicon oxide film and a silicon nitridefilm (silicon nitride oxide film) are stacked on the gate electrodeside. In this structure, since the gate electrode is in contact with thesilicon nitride film, deterioration due to oxidation can be prevented.

The first semiconductor film 222 is formed using a film having any stateof semiconductors selected from an amorphous semiconductor (AS), asemi-amorphous semiconductor in which an amorphous state and acrystalline state are mixed (also referred to as a SAS), amicrocrystalline semiconductor in which a crystal grain of 0.5 nm to 20nm can be observed in an amorphous semiconductor, and a crystallinesemiconductor. Specifically, a microcrystalline state in which a crystalgrain of 0.5 nm to 20 nm can be observed is referred to as microcrystal(μc). In any case, a semiconductor film mainly containing silicon,silicon germanium (SiGe), or the like with a thickness of 10 nm to 60 nmcan be used.

The SAS means a semiconductor having an intermediate structure betweenan amorphous structure and a crystalline structure (including a singlecrystal and a polycrystal) and having a third state which is stable interms of free energy. The SAS includes a crystalline region havingshort-range order and lattice distortion. A crystalline region of 0.5 nmto 20 nm can be observed in at least a part of the film. When silicon iscontained as a main component, a Raman spectrum is shifted to the sideof a wavenumber lower than 520 cm⁻¹. A diffraction peak of (111) or(220) to be caused by a crystal lattice of silicon is observed in X-raydiffraction. In addition, the SAS contains hydrogen or halogen of 1atomic % or more to terminate a dangling bond.

The SAS can be obtained by performing glow discharge decomposition on asilicide gas. SiH₄ is given as a typical silicide gas. In addition,Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄, or the like can also be used as thesilicide gas. The silicide gas may be diluted with hydrogen or fluorine,or hydrogen or fluorine and one or more rare gas elements of helium,argon, krypton and neon, thereby making formation of the SAS easy. Atthis time, the silicide gas is preferably diluted so that a dilutionratio thereof ranges from 10 times to 1000-times. Alternatively, the SAScan be formed using Si₂H₆ and GeF₄ diluted with a helium gas. Thereactive formation of a film by glow discharge decomposition ispreferably performed under a low pressure and may be performed withpressures in the range of approximately 0.1 Pa to 133 Pa. High-frequencypowers of 1 MHz to 120 MHz, preferably, 13 MHz to 60 MHz may be suppliedto perform glow discharge. A substrate temperature is preferably 300° C.or less, and a recommended substrate temperature is 100° C. to 250° C.

A crystalline semiconductor film can be formed by crystallizing anamorphous semiconductor film or a SAS by heating or laser irradiation.Alternatively, a crystalline semiconductor film may be directly formed.In this case, a crystalline semiconductor film can be directly formedusing a fluorine gas such as GeF₄ or F₂ and a silane gas such as SiH₄ orSi₂H₆ and utilizing heat or plasma.

The second semiconductor film 223 is conductive. An element belonging toGroup 15 of the periodic table, typically, phosphorus or arsenic isadded in the case of forming an n-channel TFT. An element belonging toGroup 13, typically, boron is added in the case of forming a p-channelTFT. The second semiconductor film is formed by a plasma CVD methodusing a silicide gas mixed with a gas including an element belonging toGroup 13 or 15 such as boron, phosphorus, or arsenic. Further, thesecond conductive semiconductor film can be formed after forming asemiconductor film, coating the semiconductor film with a solutionincluding an element belonging to Group 13 or 15, and irradiating thesolution with a laser beam. A laser beam emitted from a known pulsedlaser or continuous wave laser is appropriately used as the laser beam.

Subsequently, a first mask pattern 224 is formed over the secondsemiconductor film 223. The first mask pattern is preferably formed of aheat resistant high molecular weight material. It is preferably formedby discharging a high molecular weight material which has an aromaticring or a heterocyclic ring as a main chain and includes at least ahighly polar heteroatom group in an aliphatic moiety by a dropletdischarging method. As a typical example of such a high molecular weightmaterial, polyimide, polybenzimidazole, or the like can be used. In thecase of using polyimide, the first mask pattern 224 can be formed bydischarging a solution including polyimide from a discharge opening ontothe second semiconductor film 223 and then baking it at 200° C. for 30minutes.

Next, the second semiconductor film 223 is etched using the first maskpattern 224 to form a second semiconductor region 232 as shown in FIG.4D. Then, the first semiconductor film 222 is etched using the firstmask pattern 224 to form a first semiconductor region 231. Thereafter,the first mask pattern is removed.

The first semiconductor film and the second semiconductor film can beetched using a chlorine based gas typified by Cl₂, BCl₃, SiCl₄, CCl₄, orthe like, a fluorine based gas typified by CF₄, SF₆, NF₃, CHF₃, or thelike, or O₂.

Next, second patterns 251 and 252 to serve as source and drainelectrodes are formed using a conductive material over the secondsemiconductor region 232. Here, a solution of Ag paste dispersed withsilver particles of several run is selectively discharged. Then, partsof the second patterns 251 and 252 are irradiated with laser light usinga laser beam directly-drawing apparatus to form second conductive layers261 and 262 as shown in FIG. 4F. The second conductive layer is aconductive layer in which metal particles are baked, similarly to thefirst conductive layer. An organic resin layer dispersed with metalparticles may be formed on the opposite sides of the second conductivelayer.

Then, an exposed portion of the second semiconductor region 232 isetched using the second conductive layers 261 and 262 as masks to besectioned, thereby forming source and drain regions 254 and 255. At thistime, an exposed portion of the first semiconductor region 231 ispartially etched in some cases.

When the first semiconductor region is formed from SAS, a structure inwhich the source and drain regions cover the gate electrode can beemployed as in this embodiment mode. In place of the structure, aso-called self alignment structure in which edge portions of the sourceand drain regions are aligned with edge portions of the gate electrodecan also be employed. Further, a structure in which the source and drainregions are formed at a certain distance from the gate electrode withoutcovering it can be employed. This structure can reduce off-current.Thus, in the case of using the TFT having this structure as a switchingelement of a display device, contrast can be enhanced. Furthermore, aTFT may be formed to have a so-called multi-gate structure in which thesecond semiconductor region covers a plurality of gate electrodes. Thisstructure can also reduce off-current.

Subsequently, a passivation film is preferably formed over the secondconductive layers 261 and 262. The passivation film can be formed usingsilicon nitride, silicon oxide, silicon nitride oxide, siliconoxynitride, aluminum oxynitride, aluminum oxide, diamond like carbon(DLC), nitrogen-containing carbon (CN), or other insulating materials bya thin film formation method such as a plasma CVD method or a sputteringmethod.

Through the above described steps, a channel etch type TFT having a gateelectrode with narrow width can be manufactured. Since the semiconductorelement has a short channel length, the semiconductor element canoperate at high speed.

Embodiment Mode 3

Embodiment Mode 3 describes a channel protective type TFT of a bottomgate TFT as a semiconductor element with reference to FIGS. 5A to 5F.

As shown in FIG. 5A, a first conductive layer 211 serving as a gateelectrode and an organic resin layer 212 dispersed with metal particles,which is formed on the opposite sides of the first conductive layer 211are formed on a substrate 201 according to the same steps as inEmbodiment Mode 2. After that, a first insulating layer 221 to serve asa gate insulating film and a first semiconductor film 222 are formed.Then, a protective film 301 is formed in a region that exists over thefirst semiconductor film 222 and overlaps the first conductive layer211. The formation method and material of the protective film 301 can besimilar to those of the first mask pattern 224 shown in Embodiment Mode2.

As shown in FIG. 5B, a second semiconductor film (a conductivesemiconductor film) 302 is formed. The second semiconductor film 302 canbe formed using the same material and formation method as those of thesecond semiconductor film 223 in Embodiment Mode 2. Next, a first maskpattern 224 is formed.

The second semiconductor film is etched using the first mask pattern toform a second semiconductor region 332 as shown in FIG. 5C. In addition,a first semiconductor region 231 is formed by etching the firstsemiconductor film. After that, the first mask pattern is removed.

As shown in FIG. 5D, a second conductive layer 341 is formed using aconductive material. One or a plurality of Ag, Au, Cu, Ni, Pt, Pd, Ir,Rh, W, Al, Ta, Mo, Cd, Zn, Fe and Ti can be used as the conductivematerial. The second conductive layer 341 is formed by a known methodsuch as a CVD method, a sputtering method, a printing method, a dropletdischarging method. Here, the second conductive layer 341 is formed by asputtering method.

Subsequently, a photosensitive resin 342 is discharged or applied overthe second conductive layer 341, and then dried. A negativephotosensitive resin or a positive photosensitive resin that issensitive to ultraviolet light to infrared light is used as thephotosensitive resin.

Photosensitive resin materials such as epoxy resin, phenol resin,novolac resin, acrylic resin, melamine resin, or urethane resin are usedas the photosensitive resin. In addition, photosensitive organicmaterials such as benzocyclobutene, parylene, flare, polyimide can alsobe used. As typical positive photosensitive resins, a photosensitiveresin having phenol resin or novolac resin and a naphthoquinonediazidecompound as a photosensitive agent is given, while as typical negativephotosensitive resins, a photosensitive resin using the above mentionedresin or the like as a base resin and having diphenyl silane diol and anacid generation agent is given. In this embodiment mode, a negativephotosensitive resin is adopted.

Next, the photosensitive resin 342 is irradiated with a laser beam 343using a laser beam directly-drawing apparatus, and then developed. Asthe result thereof, second mask patterns 351 and 352 are formed as shownin FIG. 5E.

As shown in FIG. 5F, the second conductive layer 341 is etched with thesecond mask patterns 351 and 352 as masks to form source and drainelectrodes 361 and 362. In addition, the second semiconductor region 332is etched with the second mask pattern as a mask to form source anddrain regions 363 and 364. By the steps, the protective film 301 isexposed.

The formation method of the source and drain electrodes is not limitedto the method shown in this embodiment mode, and the method shown inEmbodiment Mode 2 may be adopted. Further, the forming steps of thesource and drain electrodes in this embodiment mode may be applied inEmbodiment Mode 2.

Through the above described steps, a channel protective type TFT havinga gate electrode with a narrow width can be manufactured. Since thesemiconductor element has a short channel length, the semiconductorelement can operate at high speed.

Embodiment Mode 4

Embodiment Mode 4 describes a manufacturing method of a staggered typeTFT of a top gate TFT with reference to FIGS. 6A to 6F.

As shown in FIG. 6A, first patterns 401 and 402 are formed on asubstrate 201. As the material and formation method thereof, the samematerial and formation method as those of the first pattern 102 inEmbodiment Mode 1 can be used appropriately. Next, the first patterns401 and 402 are irradiated with laser light 403. Here, laser light isemitted in the direction of an arrow 404 to form first conductive layers411 and 412 in which metal particles are baked as shown in FIG. 6B.

Then, a first semiconductor film 413 that is conductive is formed overthe first conductive layer. The first semiconductor film 413 can beformed using the same material and formation method as those of thesecond semiconductor film 222 in Embodiment Mode 2. First mask patterns414 and 415 are formed over the first semiconductor film 413. The firstmask patterns can be formed appropriately by the same formation methodand material as those of the first mask pattern 224 shown in EmbodimentMode 2.

As shown in FIG. 6C, the first semiconductor film is etched using thefirst mask pattern to form first semiconductor regions 416 and 417. Notethat the first semiconductor regions serve as source and drain regions.Then, a second semiconductor film 421 is formed. The secondsemiconductor film 421 can be formed appropriately by the same formationmethod and material as those of the first semiconductor film 222 shownin Embodiment Mode 2.

A surface of a part of the second semiconductor film 421 is irradiatedwith laser light using a laser beam directly-drawing apparatus to form asilicon oxide film 431 as shown in FIG. 6D. The silicon oxide film 431serves as a mask for etching the second semiconductor film 421. Anexposed portion of the second semiconductor film is etched with TMAH(tetramethyl ammonium hydroxide) to form a second semiconductor region441 as shown in FIG. 6E. Here, the second semiconductor film isirradiated with laser light using a laser beam directly-drawingapparatus to oxygenate a desired region, thereby forming a silicon oxidefilm. Accordingly, a semiconductor region can be formed in a desiredregion without a known photolithography process. Irradiated area of thelaser light can be reduced by decreasing a spot diameter of the laserbeam. In other words, a silicon oxide film having a minute shape and thesemiconductor region to be formed using the silicon oxide film as a maskcan be formed. Therefore, high integration of a semiconductor element ispossible. In addition, the silicon oxide film is formed by one timeirradiation of laser light having a shape corresponding to asemiconductor region (a rectangle shape, a circular shape, a desiredshape or the like), thereby enhancing throughput.

As shown in FIG. 6E, a second pattern 442 is formed over a silicon oxidefilm 431. The silicon oxide film 431 serves as a gate insulating film.Note that an insulating layer to serve as a gate insulating film may beformed anew, appropriately using the same method and material as thefirst insulating layer 221 in Embodiment Mode 2, after removing thesilicon oxide film 431. The second pattern 442 is irradiated with laserlight 443 to form a second conductive layer 451 in which metal particlesare baked and organic resin layers 452 and 453 in which metal particlesare dispersed as shown in FIG. 6E The second conductive layer 451functions as a gate electrode.

A staggered type TFT can be formed through the above described steps.

Embodiment Mode 5

Embodiment Mode 5 describes a manufacturing method of a coplanar typeTFT of a top gate TFT with reference to FIGS. 7A to 7E.

As shown in FIG. 7 A, a first insulating layer 501 is formed on asubstrate 201. The first insulating layer 501 serves as a blocking filmfor preventing impurities from the substrate from spreading into asemiconductor region to be formed later. Accordingly, a base film of aninsulating film such as a silicon oxide film, a silicon nitride film ora silicon oxynitride film is formed as the first insulating film 501.The base film has a structure of a single layer or a stacked layer oftwo or more layers.

A semiconductor film 502 is formed over the first insulating layer 501.A semiconductor film having an amorphous structure is formed by a knownmethod (such as a sputtering method, an LPCVD method or a plasma CVDmethod) as the semiconductor film 502. Thereafter, a crystallinesemiconductor film obtained by performing a known crystallizationtreatment (such as a laser crystallization method using laser lightemitted from a pulsed laser, a thermal crystallization method, a thermalcrystallization method using a metal catalyst such as nickel) or theSAS, the AS, or the like described in Embodiment Mode 2 is formed.

Then, a desired region of the semiconductor film 502 is irradiated withlaser light 503 using a laser beam directly-drawing apparatus similarlyto Embodiment Mode 4 to form a silicon oxide film 511 as shown in FIG.7B. Here, a region for forming a semiconductor region later isirradiated with the laser light by scanning the laser light 503 in thedirection of an arrow 504.

The semiconductor film 502 is etched with TMAH using the silicon oxidefilm 511 as a mask to form a semiconductor region 512.

As shown in FIG. 7 C, after removing the silicon oxide film 511, asecond insulating layer 521 to serve as a gate insulating film is formedover the semiconductor region 512 and the first insulating layer 501.The second insulating layer 521 can be formed using the same materialand method as the first insulating layer 221 shown in Embodiment Mode 2.

A first pattern 522 is formed. The first pattern is formed using thesame material as the first pattern 102 shown in Embodiment Mode 1. Then,a part of the first pattern 522 is irradiated with laser light 523 andthus a first conductive layer 531 in which metal particles are baked andan organic resin layer 532 in which metal particles are dispersed can beformed as shown in FIG. 7D. Note that the first conductive layer 531serves as a gate electrode.

As shown in FIG. 7E, the semiconductor region 512 is doped withimpurities using the first conductive layer 531 and the organic resinlayer 532 dispersed with metal particles as masks. Then, after formingan insulating film containing hydrogen, the impurity element added intothe semiconductor region is activated by heating at 400 to 550° C. Inaddition, the semiconductor region is hydrogenated to form impurityregions (source and drain regions) 541 and 542. The semiconductor regioncovered with the first conductive layer 531 and the organic resin layer532 dispersed with metal particles serves as a channel formation region543. Note that a GRTA method, an LRTA method, or a laser annealingmethod can be used as the step of activation or hydrogenation in placeof the heat treatment. In addition, gettering can also be performed atthe same time as activation in the case where the semiconductor film iscrystallized using a metal element which promotes crystallization,typically, nickel.

Note that a single-gate TFT is described in this embodiment mode;however, without being limited thereto, a multi-gate TFT may also beused. In addition, a self alignment TFT is described; however, withoutbeing limited thereto, an LDD (Lightly Doped Drain) or GOLD (Gate-drainOverlapped LDD) TFT can also be used. In the LDD structure, a region towhich an impurity element is added in low concentration is providedbetween a channel formation region and a source region or drain regionformed by adding an impurity element in high concentration. The regionis referred to as an LDD region. The TFT having this structure canreduce an off-current value. In the GOLD structure, the LDD region isoverlapped with a gate electrode with a gate insulating filmtherebetween. The structure is effective in relieving an electric fieldin the vicinity of the drain and preventing deterioration due to hotcarrier injection.

An LDD region may be formed by adding an impurity element into thesemiconductor region using the organic resin layer 532 dispersed withmetal particles as a sidewall.

Then, a third insulating layer 544 is formed over the substrate. Thethird insulating layer can be formed of an inorganic insulating materialsuch as silicon oxide, silicon nitride, silicon oxynitride, aluminumoxide, aluminum nitride, or aluminum oxynitride; acrylic acid,methacrylic acid, or a derivative thereof; a heat-resistant highmolecular weight material such as polyimide, aromatic polyamide, orpolybenzimidazole; an inorganic siloxane polymer including a Si—O—Sibond formed by using a siloxane polymer based material as a startingmaterial, typified by a silica glass; or an organic siloxane polymerinsulating material in which hydrogen bonded with silicon is substitutedby an organic group such as methyl or phenyl, typified by an alkylsiloxane polymer, an alkyl silsesquioxane polymer, a hydrosilsesquioxanepolymer, or a hydroalkyl silsesquioxane polymer. The third insulatinglayer is formed by a known method such as a CVD method, a coatingmethod, or a printing method. Note that forming the third insulatinglayer by a coating method can planarize the surface of the thirdinsulating layer and is suitable for a later step of forming a pixelelectrode. Here, the third insulating layer 544 is formed by applyingalkyl siloxane polymer by a coating method and baked.

A mask pattern is formed by a droplet discharging method and parts ofthe second insulating layer 544 and the second insulating layer 521 areremoved using the mask pattern to expose parts of the impurity regions541 and 542 of the semiconductor region, and thus opening portions areformed. Second conductive layers 545 and 546 are formed in the openingportions by the method described in Embodiment Mode 2 or 3. The secondconductive layers 545 and 546 serves as source and drain electrodes.

A coplanar type TFT having a gate electrode with a narrow width can beformed through the above described steps. Since the semiconductorelement has a short channel length, the semiconductor element canoperate at high speed.

Embodiment Mode 6

Embodiment Mode 6 describes manufacturing steps of an organicsemiconductor transistor with reference to FIGS. 8A to 8D.

As shown in FIGS. 8A and 8B, after forming a first pattern 202 over asubstrate 201 similarly to Embodiment Mode 2, a part of the firstpattern 202 is irradiated with laser light 203 to form a firstconductive layer 211 in which metal particles are baked and an organicresin layer 212 in which metal particles dispersed are provided on theopposite sides of the first conductive layer 211. Here, plastic is usedfor the substrate 201.

Next, as shown in FIG. 8C, a first insulating layer 601 to serve as agate insulating film is formed over the substrate 201, the firstconductive layer 211 and the organic resin layer 212. The firstinsulating layer 601 can be formed appropriately using the material andformation method of the first insulating layer 221 shown in EmbodimentMode 2. In addition, the first insulating layer can be formed byapplying a solution having an insulating property with a dropletdischarging method, a coating method or the like. Further, the firstconductive layer 211 may be anodized to form the first insulating layer.As a typical example of the solution having an insulating property, asolution dispersed with inorganic oxide minute particles, polyimide,polyamide, polyester, acrylic, PSG (phosphosilicate glass), BPSG(borophosphosilicate glass), silicate SOG (Spin on Glass), alkoxysilicate SOG, siloxane polymer, or the like can be appropriately used.At this time, the solution having an insulating property is dried, orbaked depending on materials.

Subsequently, a second conductive layer 602 is formed. Here, the secondconductive layer 602 can be formed using the same method and material asthe second conductive layer 341 shown in Embodiment Mode 3. Then, firstmask patterns 603 and 604 are formed over the second conductive layer602. The mask patterns are formed using the same materials as the firstmask pattern 224 shown in Embodiment Mode 2. The first mask patterns 603and 604 are each a mask pattern for forming source and drain electrodeslater.

As shown in FIG. 8D, third conductive layers 611 and 612 are formed byetching the second conductive layer 602 with the first mask patterns 603and 604. The third conductive layers 611 and 612 serve as source anddrain electrodes. Then, a semiconductor region 613 is formed between thesource electrode and the drain electrode using an organic semiconductormaterial.

The semiconductor region 613 can be formed appropriately by a printingmethod, a spray method, a droplet discharging method or the like. Anetching step is not required because of this method, and thus the numberof steps can be reduced. In addition, a known organic semiconductormaterial can be used appropriately as the organic semiconductormaterial. It is preferable to use, typically, a π-conjugated highmolecular weight material whose skeleton is formed by a conjugateddouble bond. Typically, a soluble high molecular weight material such aspolythiophene, poly(3-alkylthiophene), a polythiophene derivative, orpentacene can be used.

In addition, the semiconductor region can be formed by forming andtreating a soluble precursor. As such an organic semiconductor materialformed by using a precursor, polythienylene vinylene,poly(2,5-thienylene vinylene), polyacetylene, a polyacetylenederivative, polyallylene vinylene, or the like can be given.

When a precursor is converted into an organic semiconductor, a reactivecatalyst such as a hydrogen chloride gas is added in addition to a heattreatment. Toluene, xylene, chlorobenzene, dichlorobenzene, anisole,chloroform, dichloromethane, γ-butyl lactone, butyl cellosolve,cyclohexane, NMP (N-methyl-2-pyrrolidone), cyclohexanone, 2-butanone,dioxane, dimethylformamide (DMF), THF (tetrahydrofuran), or the like canbe used as a typical solvent for dissolving such a soluble organicsemiconductor material.

A contact layer may be provided between the semiconductor region 613 andthe conductive layers 611 and 612 serving as source and drainelectrodes. As a material of the contact layer, a conductive layerformed of an organic conductive material such as polyacetylene,polyaniline, PEDOT (poly-ethylenedioxythiophen), or PSS(poly-styrenesulphonate) can be used. A conductive layer formed from ametal element can be used for the contact layer. In this case, manyorganic semiconductor materials are p-type semiconductors whichtransport holes as carriers. Therefore, it is preferable to use a metalhaving a high work function so as to have an ohmic contact with thesemiconductor layer. Specifically, it is preferable to use a metal suchas gold, platinum, chromium, palladium, aluminum, indium, molybdenum,nickel, or an alloy thereof or the like. The contact layer can be formedusing a conductive paste including such a metal or alloy by a printingmethod or a droplet discharging method.

An organic thin film transistor having a short channel structure can beformed through the above described steps.

Embodiment Mode 7

Embodiment Mode 7 describes a manufacturing method of a semiconductorelement in which the positional relation between source and drainelectrodes and a semiconductor region is different from that inEmbodiment Mode 6 with reference to FIGS. 9A to 9E.

As shown in FIGS. 9A and 9B, a first pattern 202 is formed over asubstrate 201 as in Embodiment Mode 2, and then a part of the firstpattern 202 is irradiated with laser light 203. Then, a first conductivelayer 211 in which metal particles are baked and an organic resin layerdispersed with metal particles on the opposite sides of the firstconductive layer 211 are formed.

As shown in FIG. 9C, a first insulating layer 601 to serve as a gateinsulating film is formed over the substrate 201, the first conductivelayer 211 and the organic resin layer 212. A semiconductor region 701 isformed over the first insulating layer 601. The semiconductor region 701is formed using the material and method shown in Embodiment Mode 6.

As shown in FIG. 9D, a third conductive layer 711 is formed over thefirst insulating layer 601 and the semiconductor region 701. Then, firstmask patterns 712 and 713 are formed over the second conductive layer711. The second conductive layer 602 and the first mask patterns 603 and604 shown in Embodiment Mode 6 can be used appropriately as the secondconductive layer 711 and the first mask patterns 712 and 713,respectively. The first mask patterns serve as masks for forming sourceand drain electrodes to be formed later.

As shown in FIG. 9E, the second conductive layer 711 is etched using thefirst mask patterns 712 and 713 to form source and drain electrodes 721and 722. A semiconductor element formed in this embodiment mode has aregion in which a semiconductor region 701 is sandwiched between thefirst insulating layer 601 serving as a gate insulating film and one ofthe source and drain electrodes 721 and 722.

An organic thin film transistor having a short channel structure can beformed through the above described steps.

Embodiment Mode 8

A droplet discharging apparatus which can be used for mask patternformation in the above described embodiment modes is described inEmbodiment Mode 8. In FIG. 10, a region where one panel 1930 is to beformed is shown by a dashed line over a substrate 1900.

FIG. 10 shows one mode of a droplet discharging apparatus used to form apattern of a wiring or the like. A droplet discharging means 1905 has ahead, and the head has a plurality of nozzles. The case of having threeheads (1903 a, 1903 b, and 1903 c) each of which is provided with tennozzles is described in this embodiment mode. However, the number ofnozzles and heads can be set in accordance with a treatment area, aprocess, or the like.

The heads are connected to a control means 1907, and the control meanscontrols the heads by a computer 1910, so that a predetermined patterncan be drawn. A timing of drawing may be determined by, for example,using a marker 1911 that is formed over the substrate 1900 or the likefixed on a stage 1931 as a reference point. Alternatively, it may bedetermined with an edge of the substrate 1900 as a reference point. Thereference point is detected by an imaging means 1904 such as a CCD, andchanged into a digital converted signal by an image processing means1909. Then, the digital signal is recognized by the computer 1910, and acontrol signal is generated and transmitted to the control means 1907.When the pattern is drawn in this manner, a distance between a patternformation surface and a tip of the nozzle may be set 0.1 cm to 5 cm,preferably, 0.1 cm to 2 cm, more preferably, approximately 0.1 cm.Landing accuracy of a droplet is improved by making the distance shortas described above.

At this time, information of a pattern to be formed over the substrate1900 is stored in a storage medium 1908, and a control signal istransmitted to the control means 1907 based on this information, so thatthe heads 1903 a, 1903 b, and 1903 c can be individually controlled. Inother words, droplets including different compositions can be dischargedfrom each nozzle of the heads 1903 a, 1903 b, and 1903 c. For example,the nozzles of the heads 1903 a and 1903 b can discharge a dropletincluding a composition for an insulating film and the nozzles of thehead 1903 c can discharge a composition for a conductive film.

Further, the nozzles of the head can also be individually controlled.Since the nozzles can be individually controlled, different compositionscan be discharged from specific nozzles. For example, one head 1903 acan be provided with a nozzle which discharges a droplet including acomposition for a conductive film and a nozzle which discharges adroplet including a composition for an insulating film.

Note that the nozzles are connected to a tank filled with compositions.

In the case of performing a droplet discharging treatment on a largearea, like a formation step of an interlayer insulating film, dropletsincluding a composition for an interlayer insulating film are preferablydischarged from all nozzles. Further, droplets including a compositionfor an interlayer insulating film are preferably discharged from allnozzles of a plurality of heads. Accordingly, throughput can beimproved. Naturally, in the interlayer insulating film formation step, adroplet discharging treatment may be performed on a large area bydischarging a droplet including a composition for an interlayerinsulating film from one nozzle and by moving the nozzle over thesubstrate a plurality of times.

Pattern formation on a large mother glass can be performed by moving thehead in zigzag or shuttling the head. At this time, the head may bemoved relative to the substrate a plurality of times. When the head ismoved over the substrate, the head is preferably provided at a slightangle to the moving direction.

When a plurality of panels is formed out of the large mother glass, thehead preferably has a width almost equal to that of one panel. This isbecause a pattern can be formed in the region where one panel 1930 is tobe formed by moving the head once; thus, high throughput can beexpected.

The head may have a width narrower than that of the panel. At this time,a plurality of heads having a narrow width may be arranged in series tohave a width almost equal to that of one panel. Bending of the heads,which is concerned when a width of the head becomes broader, can beprevented from occurring by arranging the plurality of heads having anarrow width in series. Naturally, a pattern may be formed by moving ahead having a narrow width a plurality of times.

A piezo method can be employed as a droplet discharging method. Thepiezo method is utilized also in an inkjet printer since it has superiordroplet controllability and a high degree of freedom for ink selection.Note that the piezo method includes a bender type (typically, an MLP(Multi Layer Piezo) type), a piston type (typically, an MLChip (MultiLayer Ceramic Hyper Integrated Piezo Segments) type), a side wall type,and a roof wall type. Further, a droplet discharging method using athermal method, by which a heating element generates heat to generatebubbles and a solution is pushed out, may be employed depending on asolvent of the solution.

Embodiment 1

In Embodiment 1, a resistance value of a sample formed by forming apattern using Ag paste and baking the pattern temporarily and aresistance value of a sample formed by forming a pattern using Ag pasteand baking Ag particles of the pattern by laser irradiation aredescribed with reference to FIGS. 32A and 32B.

A resistance value of a sample formed by dropping Ag paste on a glasssubstrate by a droplet discharging method and baking it temporarilyaccording to Condition 1 and a resistance value of a sample bakedaccording to Condition 2 are compared. Obtained results are shown inTable 1, and the graph thereof is shown in FIG. 32A. The shape of eachsample whose resistance value is measured is an elliptical shape whosemajor axis D1 is 1000 μm long and minor axis D2 is 200 μm wide as shownFIG. 32B. Note that Condition 1 is to heat for 30 minutes at 100° C.Condition 2 is to emit laser light oscillated from a continuous waveYVO₄ laser (laser power of 2 W, a laser beam diameter of 80 μm, andlaser light with wavelength of 532 nm). At this time, the scan speed is500 mm/sec.

TABLE 1 condition 1 condition 2 resistance 2.00E+07 7.77E+01 value/Ω2.00E+07 1.14E+02 1.00E+07 1.00E+02 2.00E+07 9.56E+01 1.00E+07 8.88E+01

As apparent from Table 1 and FIGS. 32A and 32B, the resistance value ofthe sample is reduced due to the treatment according to Condition 2. Inother words, it is possible to reduce the resistance value by bakingmetal particles with laser irradiation on paste containing metalparticles.

Embodiment 2

Next, manufacturing methods of an active matrix substrate and a displaypanel including the active matrix substrate are described with referenceto FIGS. 12A to 12C, 13A to 13C, 14A to 14C, 15A, 15B and 16. InEmbodiment 2, a liquid crystal display panel is taken as an example ofthe display panel. FIG. 16 is a top view of the active matrix substrate,while FIGS. 12A to 12C, 13A to 13C, 14A to 14C, 15A and 15B each shows avertical cross-sectional view corresponding to A-B of a connectionterminal portion and C-D of a pixel portion.

As shown in FIG. 12A, an insulating film 801 with thickness of 100 nm isformed by oxidizing the surface of a substrate 800 at 400° C.Subsequently, a first conductive layer 802 is formed on the insulatingfilm 801. A light-transmitting conductive film or a reflectiveconductive film are typical examples of the first conductive layer 802.As materials of the light-transmitting conductive film, indium tin oxide(ITO), zinc oxide (ZnO), indium zinc oxide (IZO), gallium-doped zincoxide (GZO), indium tin oxide including silicon oxide and the like aregiven. In addition, as materials of the reflective conductive film, ametal such as aluminum (Al), titanium (Ti), silver (Ag), or tantalum(Ta), a metal material including the metal and nitrogen with aconcentration of a stoichiometric composition ratio or less, titaniumnitride (TiN) or tantalum nitride (TaN) that is nitride of the metal,aluminum containing nickel of 1% to 20% and the like are given. Thefirst conductive layer 802 is formed appropriately by a sputteringmethod, an evaporation method, a CVD method, a coating method or thelike. Here, an AN100 glass substrate manufactured by Asahi Glass Co.,Ltd. is used as the substrate 800. Indium tin oxide (ITO) containingsilicon oxide is formed as the first conductive layer 802 by asputtering method to have a thickness of 110 nm.

Then, a first mask pattern 803 is formed over the first conductive layer802 by a droplet discharging method. The first mask pattern serves as amask for forming a second mask pattern (a film serving as a mask foretching a conductive layer) later. Accordingly, the first mask patternpreferably has a low wettability. In other words, it is preferable thatthe surface of the first mask pattern easily repels the second maskpattern to be formed later. Here, the first mask pattern is formed usinga solution in which a fluorine-based silane coupling agent is dissolvedin an alcohol solvent.

Subsequently, a second mask pattern 804 is formed by a dropletdischarging method. A material having high wettability is discharged bythe droplet discharging method to form the second mask pattern 804.Polyimide is discharged by the droplet discharging method and heated tobe baked for 30 minutes at 200° C., thereby forming the second maskpattern 804.

A relationship between a region having low wettability and a regionhaving high wettability is described here with reference to FIG. 30. Theregion having low wettability (here, the first mask pattern 803) means aregion having a large contact angle θ1 between the surface and liquid asshown in FIG. 30. Liquid is repelled in a hemispherical shape by thesurface. On the other hand, the region having high wettability (here,the second mask pattern 804) means a region having a small contact angleθ2 between the surface and liquid on the surface. Liquid is spread onthe surface.

When two regions having different contact angles are in contact witheach other, a region having a relatively small contact angle becomes aregion having high wettability and a region having a relatively largecontact angle becomes a region having low wettability. When the tworegions are coated or discharged with a solution, the solution is spreadover the region having low wettability and is repelled in ahemispherical shape at the interface with the region having highwettability.

A difference between the contact angle θ1 of the region having lowwettability and the contact angle θ2 of the region having highwettability is preferably 30°, desirably, 40° or more. Accordingly, amaterial of the region having high wettability is repelled in ahemispherical shape by the surface of the region having low wettability.Each mask pattern 803 and 804 can be formed in a self-alignment manner.

Next, after the first mask pattern 803 is removed by ashing usingoxygen, the first conductive layer 802 that is not covered with thesecond mask pattern 804 is removed by etching as shown in FIG. 12B. Thesecond mask pattern 804 is removed to form a second conductive layer805. The second conductive layer 805 serves as a pixel electrode.

First patterns 811 and 812 are formed as shown in FIG. 12C. The firstpatterns 811 and 812 are formed by discharging a composition containingorganic resin and metal particles such as Ag, Au, Cu, Ni, Pt, Pd, Ir,Rh, W, Al, Ta, Mo, Cd, Zn, Fe, Ti, Si, Ge, Zr, or Ba by a dropletdischarging method.

Parts of the first patterns 811 and 812 are irradiated with laser light813 and 814 to form third conductive layers 815 and 816 in which metalparticles are baked as shown in FIG. 13A. At this time, regions that arenot irradiated with the laser light in the first patterns 811 and 812are organic resin layers 817 and 818 dispersed with metal particles. Thethird conductive layers 815 and 816 are to serve as a gate wiring and agate electrode, respectively.

Then, a gate insulating film 821 is formed by a sputtering method. Asilicon nitride oxide film (SiNO, N>O) of 110 nm thick is formed as thegate insulating film 821.

A first semiconductor film 822 and a second semiconductor film 823 thatis n-type are formed. An amorphous silicon film of 150 nm thick isformed by a sputtering method as the first semiconductor film 822. Then,an oxide film on the surface of the amorphous silicon film is removed,and then a semi-amorphous silicon film of 50 nm thick is formed as thesecond semiconductor film 823 by the same method. Here, since the firstsemiconductor film and the second semiconductor film are formed by asputtering method, the films can be formed at a room temperature.

Then, third mask patterns 824 and 825 are formed over the secondsemiconductor film. Polyimide is discharged on the second semiconductorfilm by a droplet discharging method and heated for 30 minutes at 200°C. to form the third mask patterns. The third mask patterns 824 and 825are formed over a region where a first semiconductor region is to beformed later.

As shown in FIG. 13B, the second semiconductor film 823 is etched usingthe third mask patterns to form a second semiconductor region 826(source and drain regions, a contact layer). The second semiconductorfilm is etched using a mixture gas whose flow ratio of CF₄:O₂ is 10:9.After that, the third mask patterns 824 and 825 are removed by aseparation liquid.

A fourth mask pattern 831 for covering the second semiconductor region826 and the first semiconductor film 822 formed between the secondsemiconductor regions is formed. The fourth mask pattern is formed usingthe same material and method as the third mask pattern. The firstsemiconductor film 822 is etched using the fourth mask pattern to form afirst semiconductor region 832 as shown in FIG. 13C and to expose a partof the gate insulating film 821. The first semiconductor film is etchedusing a mixture gas whose flow ratio of CF₄:O₂ is 10:9, and then ashingusing oxygen is conducted. After that, the fourth mask pattern 831 isremoved by a separation liquid.

As shown in FIG. 14A, fifth mask patterns 841 and 842 are formed. Asolution having low wettability is discharged onto a region where thegate insulating film 821 and the second conductive layer 805 areoverlapped and onto a connection terminal portion by a dropletdischarging method to form fifth mask patterns. Here, a solution of afluorine-based silane coupling agent dissolved in an alcohol solvent isused as the solution having low wettability. The fifth mask patterns 841and 842 are each a protective film for forming a sixth mask pattern usedto form a contact hole in a region where a drain electrode is to beconnected to the second conductive layer 805. The sixth mask pattern isalso a protective film for exposing the conductive layer of theconnection terminal portion.

The sixth mask pattern 843 is formed. The sixth mask pattern is a maskfor forming a contact hole and is formed by discharging polyimide by adroplet discharging method and heating it at 200° C. for 30 minutes. Atthis time, the fifth mask pattern 841 is formed of a material having lowwettability and the sixth mask pattern 843 is formed of a materialhaving high wettability. Therefore, the sixth mask pattern 843 is notformed in the region where the fifth mask pattern is formed.

The fifth mask patterns 841 and 842 are removed by oxygen ashing toexpose a part of the gate insulating film 821. Then, a part of theexposed gate insulating film is etched using the sixth mask pattern 843to form a contact hole 844. The gate insulating film is etched usingCHF₃. After that, the sixth mask pattern is removed by oxygen ashing andetching using a separation liquid.

Fourth conductive layers 851 and 852 are formed by a droplet dischargingmethod as shown in FIG. 14C. The fourth conductive layers 851 and 852serve as source and drain wiring layers. A composition dispersed with Ag(silver) particles is discharged and dried by heating at 100° C. for 30minutes and thereafter baked by laser irradiation to form the fourthconductive layers 851 and 852.

Through the above described steps, an active matrix substrate can beformed. Note that a plane structure corresponding to a verticalcross-sectional structure taken along line A-B and line C-D in FIG. 14Cis shown in FIG. 16, and thus FIG. 16 may be referred to as well.

A protective film 861 is formed as shown in FIG. 15A. A silicon nitridefilm having a thickness of 100 nm is formed as the protective film by asputtering method using a silicon target and argon and nitrogen (a flowratio of Ar:N₂=1:1) as a sputtering gas.

Subsequently, an insulating film is formed by a printing method or aspin coating method to cover the protective film 861. Then, rubbing isperformed to form an orientation film 862. Note that the orientationfilm 862 can be formed by an oblique evaporation method.

A sealing agent 871 in the shape of a closed loop is formed by a dropletdischarging method in a peripheral region of the pixel portion, in anopposite substrate 881 provided with an orientation film 883 and asecond pixel electrode (opposite electrode) 882. A liquid crystalmaterial is dropped by a dispenser method (dropping method) inside theclosed loop formed by the sealing agent 871.

The sealing agent 871 may be mixed with filler. Moreover, a colorfilter, a shielding film (black matrix) or the like may be provided forthe opposite substrate 881.

Here, a step of dropping a liquid crystal material is described withreference to FIGS. 17A and 17B. FIG. 17A is a perspective view showing astep of dropping a liquid crystal material with a dispenser 2701, andFIG. 17B is a cross-sectional view taken along a line A-B in FIG. 17A.

A liquid crystal material 2704 is dropped or discharged from thedispenser 2701 to cover a region 2703 surrounded by a sealing agent2702. A liquid crystal layer can be formed by moving the dispenser 2701or by moving a substrate 2700 with the dispenser 2701 fixed. Inaddition, a plurality of dispensers 2701 may be provided to drop theliquid crystal material onto a plurality of regions simultaneously.Consequently, as shown in FIG. 17B, the liquid crystal material 2704 canbe selectively dropped or discharged only onto a region surrounded bythe sealing agent 2702.

Here, the liquid material is dropped in a pixel portion. However, asubstrate having the pixel portion may be attached after a liquidmaterial is dropped on an opposite substrate side.

Subsequently, as shown in FIG. 15A, the opposite substrate 881 providedwith the orientation film 883 and the second pixel electrode (oppositeelectrode) 882 is attached to the active matrix substrate andultraviolet curing is performed in vacuo. Thus, a liquid crystal layer884 filled with the liquid crystal material is formed. A dipping method(a pumping method) that injects a liquid crystal material using acapillary phenomenon, after attaching the opposite substrate, can beused as a method for forming the liquid crystal layer 884, instead of adispenser method (a dropping method).

In the case where an insulating film is formed over each edge portion ofthe third conductive layer 815 and a source wiring layer (not shown),after removing the insulating film, a connection terminal (a connectionterminal 886 to be connected to the third conductive layer, and aconnection terminal to be connected to the source wiring layer is notshown) is attached with a conductive layer 885 therebetween as shown inFIG. 15B. Further, a connection portion of each wiring layer andconnection terminal is preferably sealed with a sealing resin. Thisstructure can prevent moisture from a section from entering anddeteriorating the pixel portion. Through the above described steps, aliquid crystal display panel can be formed.

Through the above described steps, a liquid crystal display panel can bemanufactured. Note that a protective circuit, typically, a diode or thelike for preventing electrostatic damage may be provided between theconnection terminal and the source wiring (gate wiring) or in the pixelportion. In this case, electrostatic damage can be prevented bymanufacturing it according to a similar step to that of theabove-described TFT and connecting the gate wiring layer of the pixelportion to the drain or source wiring layer of the diode.

Note that any of Embodiment Modes 1 to 8 can be applied to thisembodiment.

Embodiment 3

A method for manufacturing a light emitting display panel as a displaypanel is described in Embodiment 3 with reference to FIGS. 19A and 19B,20A and 20B, 21A and 21B and 22. A plane structure of a pixel portion isshown in FIG. 22, and FIGS. 19A and 19B, 20A and 20B, 21A and 21B and 22schematically show a vertical cross-sectional structure corresponding toa line A-B and a line C-D of the pixel portion in FIG. 22.

A first insulating layer 2002 is formed over a substrate 2001 to have athickness of 100 nm to 1000 nm as shown in FIG. 19A. Here, the firstinsulating layer 2002 is formed by stacking a silicon oxide film of 100nm thick formed by a plasma CVD method and a silicon oxide film of 480nm thick formed by a low-pressure thermal CVD method.

An amorphous semiconductor film is formed to have a thickness of 10 to100 nm. Here, an amorphous silicon film is formed by a low-pressurethermal CVD method to have a thickness of 50 nm. The amorphous siliconfilm is crystallized. In this embodiment, the amorphous silicon film isirradiated with laser light to form a crystalline silicon film. Anunnecessary portion of the crystalline silicon film is removed to formsemiconductor regions 2003 and 2004. A second insulating layer 2005serving as a gate insulating film is formed. Here, a silicon oxide filmis formed as the second insulating layer 2005 by a CVD method.

A channel doping step of adding a p-type or n-type impurity element inlow concentration to a region to become a channel region of a TFT isentirely or selectively performed. This channel doping step is a stepfor controlling a threshold voltage of the TFT. Note that boron is addedby an ion doping method in which diborane (B₂H₆) is plasma-activatedwithout mass separation. Naturally, an ion implantation method with massseparation may be used.

First patterns 2006 to 2009 are formed and then, irradiated with laserlight 2010 to 2013 to form first conductive layers 2014 to 2016 servingas gate electrodes and to form a first conductive layer 2017 serving asa capacitor wiring as shown in FIG. 19B. At the same time as this step,organic resin layers 2018 to 2021 dispersed with metal particles areformed in regions that are not irradiated with the laser light 2010 to2013. Here, Ag paste is discharged by a droplet discharging method andirradiated with the laser light.

As shown in FIG. 20A, high concentration impurity regions 2030 to 2034are formed by adding phosphorus into a semiconductor region in aself-alignment manner with the first conductive layers 2014 to 2017 andthe organic resin layers 2018 to 2021 dispersed with metal particles asmasks. The concentration of phosphorus in the high concentrationimpurity region is adjusted to be 1×10²⁰ to 1×10²¹ atoms/cm³ (typically,2×10²⁰ to 5×10²⁰ atoms/cm³). Note that regions that are overlapped withthe first conductive layers 2014 to 2017 and the organic resin layers2018 to 2021 dispersed with metal particles in the semiconductor regions2003 and 2004 become a channel formation region.

A third insulating layer 2035 is formed to cover the first conductivelayers 2014 to 2017. Here, an insulating film containing hydrogen isformed. Thereafter, the impurity element added to the semiconductorregions is activated and the semiconductor regions are hydrogenated.Here, a silicon nitride oxide film (SiNO film) obtained by a sputteringmethod is used as the insulating film containing hydrogen.

Second conductive layers 2041 to 2044 are formed after opening portionsare formed to reach the semiconductor regions. The second conductivelayers 2041, 2042, 2043 and 2044 serve as a source wiring, a firstconnection wiring, a power supply line, and a second connection wiring,respectively. In this embodiment, a stacked film having a three-layerstructure is formed by sequentially stacking a Ti film, analuminum-silicon alloy film, and a Ti film by a sputtering method and isetched into a desired shape to form the second conductive layers.

A fourth insulating layer 2051 is formed as shown in FIG. 20B. Aninsulating layer which can be planarized is preferable for the fourthinsulating layer. The insulating layer which can be planarized can beformed appropriately using the same material and method as the thirdinsulating layer 544 shown in Embodiment Mode 5. Here, acrylic resin isformed. Note that stray light from a light emitting element to be formedlater is absorbed by the fourth insulating layer, when an organicmaterial in which a material absorbing visible light such as a blackpigment or a coloring matter is dissolved or dispersed is used for thefourth insulating layer; thus, the contrast of each pixel can beenhanced.

An opening portion is formed in the fourth insulating layer by knownphotolithography and etching, and a part of the second conductive layer2044 (the second connection wiring) is exposed. Then, a third conductivelayer 2052 is formed. The third conductive layer 2052 is formed bystacking a reflective conductive film and a transparent conductive film.Here, an aluminum film containing nickel of 1% to 20% and ITO containingsilicon oxide are stacked by a sputtering method. Note that the aluminumcontaining nickel of 1% to 20% is preferable because it is notelectrically corroded even when in contact with ITO that is oxide.

A first mask pattern 2053 is formed by a droplet discharging method. Asecond mask pattern 2054 is formed by a droplet discharging method. Thefirst mask pattern 2053 is formed by discharging a material having lowwettability, here, a solution of a fluorine-based silane coupling agentdissolved in an alcohol solvent by a droplet discharging method.Polyimide is discharged by a droplet discharging method and baked byheating it at 200° C. for 30 minutes to form the second mask pattern2054.

After the first mask pattern 2053 is removed by ashing using oxygen, aportion of the third conductive layer 2052 which is not covered with thesecond mask pattern 2054 is removed by etching as shown in FIG. 21A. Thesecond mask pattern 2054 is removed to form a fourth conductive layer2055. The fourth conductive layer 2055 serves as a first pixelelectrode. Note that a plane structure corresponding to a verticalcross-sectional structure taken along a line A-B and a line C-D in FIG.21A is shown in FIG. 22, and thus FIG. 22 may be referred to as well.

A fifth insulating layer 2061 to be a bank (also referred to as apartition wall, a mound or the like) is formed to cover an edge portionof the fifth conductive layer 2055. A photosensitive ornon-photosensitive organic material (polyimide, acrylic, polyamide,polyimide amide, and benzocyclobutene or resist) or a SOG film (forexample, a SiOx film including an alkyl group) having a thickness of 0.8μm to 1 μm is used as the fifth insulating layer. It is preferable toform the fifth insulating layer 2061 using a photosensitive material,because a side face thereof becomes such a shape that the radius ofcurvature continuously changes and an upper-layer thin film is formedwithout break.

The fifth insulating layer 2061 may be a light shielding insulator inwhich a material absorbing visible light such as a coloring matter or ablack pigment is dissolved or dispersed in the above-described organicmaterial. For example, a material such as COLOR MOSAIC CK (trade name)manufactured by FUJIFILM OLIN Co., Ltd. is used. In this case, the fifthinsulating layer serves as a black matrix; thus, the fifth insulatinglayer can absorb stray light from a light emitting element to be formedlater. Accordingly, the contrast of each pixel can be enhanced. Further,the fourth insulating layer 2051 that is also formed of alight-shielding insulator can generate a light-shielding effect whencombined with the fifth insulating layer 2061.

A layer including a light emitting material 2062 is formed over thesurface of the fourth conductive layer 2055 and over the edge portion ofthe fifth insulating layer 2061 by an evaporation method, a coatingmethod, a droplet discharging method, or the like. A fifth conductivelayer 2063 serving as a second pixel electrode is formed over the layerincluding a light emitting material 2062. Here, ITO containing siliconoxide is formed by a sputtering method. Accordingly, the fourthconductive layer 2055, the layer including a light emitting material2062, and the fifth conductive layer 2063 can form a light emittingelement. Each material of the conductive layer constracting a lightemitting element and the layer including a light emitting material isappropriately selected and each thickness thereof is adjusted.

Note that water adsorbed inside or on the surface of the fifthinsulating layer 2061 is removed by performing a heat treatment at 200°C. at atmospheric pressure before forming the layer including a lightemitting material 2062. In addition, a heat treatment is preferablyperformed at 200° C. to 400° C., preferably, 250° C. to 350° C. underlow pressure, and the layer including a light emitting material 2062 ispreferably formed by a vacuum evaporation method or a dropletdischarging method under low pressure without being exposed toatmospheric air.

The layer including a light emitting material 2062 may be formed of acharge injection transport material and a light emitting materialcontaining an organic compound or an inorganic compound. The layerincluding a light emitting material may include one or plural kinds oflayers of a low molecular weight organic compound, an intermediatemolecular weight organic compound typified by dendrimer, oligomer, orthe like, and a high molecular weight organic compound, which areclassified depending on the number of molecules. The layer including alight emitting material may be combined with an electron injectiontransport or hole injection transport inorganic compound.

As a highly electron transporting material among charge injectiontransport materials, a metal complex having a quinoline skeleton or abenzoquinoline skeleton such as tris(8-quinolinolato)aluminum [Alq₃],tris(4-methyl-8-quinolinolato) aluminum [Almq₃],bis(10-hydroxybenzo[h]-quinolinato) beryllium [BeBq₂], or bis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum [BAlq], or thelike can be used.

As a highly hole transporting material, an aromatic amine compound (inother words, a compound having a benzene ring-nitrogen bond) such as4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl [α-NPD],4,4′-bis[N-(3-methylphenyl)-N-phenyl-amino]-biphenyl [TPD],4,4′,4″-tris(N,N-diphenyl-amino)-triphenylamine [TDATA], or4,4′,4″-tris[N-(3-methylphenyl)-N-phenyl-amino]-triphenylamine [MTDATA]can be used.

As a highly electron injecting material among charge injection transportmaterials, a compound of alkali metal or alkaline earth metal such aslithium fluoride (LiF), cesium fluoride (CsF), or calcium fluoride(CaF₂) can be specifically used. The highly electron injecting materialmay be a mixture of a highly electron transporting material such as Alq₃and an alkaline earth metal such as magnesium (Mg).

As a highly hole injecting material among charge injection transportmaterials, metal oxide such as molybdenum oxide (MoO_(x)), vanadiumoxide (VO_(x)), ruthenium oxide (RuO_(x)), tungsten oxide (WO_(x)), ormanganese oxide (MnO_(x)) can be used. In addition, a phthalocyaninecompound such as phthalocyanine (H₂Pc) or copper phthalocyanine (CuPc)can be used.

A light emitting layer may perform color display by providing each pixelwith a light emitting layer having a different emission wavelength band.Typically, a light emitting layer corresponding to each color of R(red), G (green), and B (blue) is formed. In this case, color purity canbe increased and a pixel portion can be prevented from having a mirrorsurface (glare) by providing a light emitting side of a pixel with afilter (colored layer) which transmits light of the emission wavelengthband. Providing the light emitting side of a pixel with the filter(colored layer) can omit a circularly polarizing plate or the like whichis conventionally required and can eliminate the loss of light emittedfrom the light emitting layer. Further, change in hue, which occurs whena pixel portion (display screen) is obliquely seen, can be reduced.

A light-emitting material forming the light emitting layer includesvarious materials. As to a low molecular weight organic light emittingmaterial, 4-(dicyanomethylene)2-methyl-6-[2-(1,1,7,7-tetramethyljulolidine-9-yl)ethenyl]-4H-pyran[DCJT],4-dicyanomethylene-2-tert-butyl-6-[2-(1,1,7,7-tetramethyljulolidine-9-yl-ethenyl)]-4H-pyran[DCJTB], periflanthene,2,5-dicyano-1,4-bis[2-(10-methoxy-1,1,7,7-tetramethyljulolidine-9-yl)ethenyl]benzene,N,N′-dimethylquinacridon [DMQd], coumarin 6, coumarin 545T,tris(8-quinolinolate) aluminum [Alq₃], 9,9′-bianthryl,9,10-diphenylanthracene [DPA], 9,10-di(2-naphthyl) anthracene [DNA], orthe like can be used. In addition, another material can also be used.

A high molecular weight organic light emitting material is physicallystronger than a low molecular weight material and is superior indurability of the element. In addition, a high molecular weight materialcan be formed by a coating method, and therefore, the element isrelatively easily manufactured. Alight emitting element using a highmolecular weight organic light emitting material basically has the samestructure as that of a light emitting element using a low molecularweight organic light emitting material, in other words, a cathode, alayer including a light emitting material and an anode. However, atwo-layer structure is employed in many cases when the layer including alight emitting material using a high molecular weight organic lightemitting material is formed. This is because it is difficult to formsuch a stacked structure as that in the case of using a low molecularweight organic light emitting material. Specifically, the light emittingelement using a high molecular weight organic light emitting materialhas a structure of a cathode, a light emitting layer, a hole transportlayer and an anode.

The emission color is determined by the material of the light emittinglayer. Therefore, a light emitting element which emits desired light canbe formed by selecting an appropriate material of the light emittinglayer. Polyparaphenylene vinylene, polyparaphenylene, polythiophen, orpolyfluorene based material can be used as a high molecular weight lightemitting material that can be used to form the light emitting layer.

A derivative of poly(paraphenylene vinylene) [PPV], for example,poly(2,5-dialkoxy-1,4-phenylene vinylene) [RO-PPV],poly(2-(2′-ethyl-hexoxy)-5-methoxy-1,4-phenylene vinylene) [MEH-PPV],poly(2-(dialkoxyphenyl)-1,4-phenylene vinylene) [ROPh-PPV], and the likecan be used as the polyparaphenylene-vinylene based light emittingmaterial. A derivative of polyparaphenylene [PPP], for example,poly(2,5-dialkoxy-1,4-phenylene) [RO-PPP],poly(2,5-dihexoxy-1,4-phenylene), and the like can be used as thepolyparaphenylene based light emitting material. A derivative ofpolythiophene [PT], for example, poly(3-alkylthiophene) [PAT],poly(3-hexylthiophene) [PHT], poly(3-cyclohexylthiophene) [PCHT], poly(3-cyclohexyl-4-methylthiophene) [PCHMT],poly(3,4-dicyclohexylthiophene) [PDCHT],poly[3-(4-octylphenyl)-thiophene] [POPT], poly[3-(4-octylphenyl)-2,2bithiophene] [PTOPT], and the like can be used as the polythiophenebased light emitting material. A derivative of polyfluorene [PF], forexample, poly(9,9-dialkylfluorene) [PDAF], poly(9,9-dioctylfluorene)[PDOF], and the like can be used as the polyfluorene based lightemitting material.

In addition, the light emitting layer can be formed to emit monochromeor white light. In the case of using a white light emitting material, afilter (colored layer) which transmits light having a specificwavelength is provided on a light emitting side of a pixel therebyperforming color display.

In order to form a light emitting layer which emits white light, forexample, Alq₃, Alq₃ partially doped with Nile Red that is a red lightemitting pigment, p-EtTAZ, and TPD (aromatic diamine) are sequentiallystacked by an evaporation method to obtain white light emission. Whenthe light emitting layer is formed by a coating method using spincoating, the layer after coating is preferably baked by vacuum heating.For example, an aqueous solution of poly(ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) may be entirelyapplied and baked to form a film that functions as a hole injectionlayer. Then, a polyvinyl carbazole (PVK) solution doped with a lightemitting center pigment (such as 1,1,4,4-tetraphenyl-1,3-butadiene(TPB), 4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran(DCM1), Nile Red, or coumarin 6) may be entirely applied and baked toform a film that functions as a light emitting layer.

The light emitting layer can be formed as a single layer.1,3,4-oxadiazole derivative (PBD) having electron transportingproperties may be dispersed in polyvinyl carbazole (PVK) having holetransporting properties. Another method for obtaining white lightemission is to disperse PBD of 30 wt % as an electron transporting agentand to disperse four kinds of pigments (TPB, coumarin 6, DCM1, and NileRed) in appropriate amounts. In addition to the light emitting elementsdescribed here that provide white light emission, a light emittingelement that can provide red light emission, green light emission, orblue light emission can be manufactured by appropriately selectingmaterials of the light emitting layer.

Note that properties of hole injection from the anode can be enhanced byinterposing a high molecular weight organic light emitting materialhaving hole transporting properties between the anode and the highmolecular weight organic light emitting material having light emittingproperties. The hole transporting material is generally dissolved intowater together with an acceptor material, and the obtained solution isapplied by a spin coating method or the like. Since the holetransporting material is insoluble in an organic solvent, a layerstacked with the above-described organic light emitting material havinglight emitting properties can be formed. A mixture of PEDOT and camphorsulfonic acid (CSA) which serves as an acceptor material, a mixture ofpolyaniline [PANI] and polystyrene sulfonic acid [PSS] which serves asan acceptor material, and the like can be used as the high molecularweight organic light emitting material having hole transportingproperties.

Further, a triplet excitation material containing a metal complex or thelike as well as a singlet excitation light emitting material may be usedfor the light emitting layer. For example, among pixels emitting red,green, and blue light, a pixel emitting red light whose luminance isreduced by half in a relatively short time is made using a tripletexcitation light emitting material and pixels emitting the other lightare made using a singlet excitation light emitting material. A tripletexcitation light emitting material has a characteristic that thematerial has a good luminous efficiency and consumes less power toobtain the same luminance. When a triplet excitation material is usedfor a red pixel, only a small amount of current is needed to be appliedto the light emitting element. Thus, reliability can be improved. Pixelsemitting red and green light may be made using a triplet excitationlight emitting material and a pixel emitting blue light may be madeusing a singlet excitation light emitting material to achieve low powerconsumption. Lower power consumption can be achieved by forming a lightemitting element which emits green light that has high visibility with atriplet excitation light emitting material.

A metal complex used as a dopant is an example of the triplet excitationlight emitting material, and a metal complex having platinum that is athird transition series element as a metal center, a metal complexhaving iridium as a metal center, and the like are known. The tripletexcitation light emitting material is not limited to the compounds. Acompound having the above-described structure and an element belongingto any one of Groups 8 to 10 of the periodic table as a metal center canalso be used.

The above-described materials for forming the layer including a lightemitting material are just examples. The light emitting element can beformed by appropriately stacking functional layers such as a holeinjection transport layer, a hole transport layer, an electron injectiontransport layer, an electron transport layer, a light emitting layer, anelectron blocking layer, and a hole blocking layer. Further, a mixedlayer or a mixed junction may be formed by combining these layers. Thelayer structure of the light emitting layer can be varied. Instead ofproviding a specific electron injection region or light emitting region,modification such as providing an electrode for a purpose or providing alight emitting material to be dispersed is acceptable as long as it doesnot apart from the scope of the present invention.

The light emitting element formed with the above-described materialemits light by being biased in a forward direction. A pixel of a displaydevice formed with a light emitting element can be driven by a simplematrix system or an active matrix system. In any system, each pixelemits light by applying a forward bias thereto at a specific timing;however, the pixel is in a non-light-emitting state for a certainperiod. Reliability of the light emitting element can be improved byapplying a reverse bias at this non-light-emitting time. In the lightemitting element, there is a deterioration mode in which emissionintensity is decreased under specific driving conditions or adeterioration mode in which a non-light-emitting region is enlarged inthe pixel and luminance is apparently decreased. However, progression ofdeterioration can be slowed down by alternating driving, in other words,by applying a forward bias and a reverse bias alternately. Thus,reliability of the light emitting device can be improved.

Subsequently, a transparent protective layer 2064 for preventing waterpenetration is formed to cover the light emitting element. A siliconnitride film, a silicon oxide film, a silicon oxynitride film (a SiNOfilm (composition ratio: N>O) or a SiON film (composition ratio: N<O)),a thin film containing carbon as its main component (for example, a DLCfilm or a CN film), or the like, which can be obtained by a sputteringmethod or a CVD method, can be used as the transparent protective layer2064.

Through the above described steps, a light emitting display panel can bemanufactured. Note that a protective circuit, typically, a diode or thelike for preventing electrostatic damage may be provided between theconnection terminal and the source wiring layer (gate wiring layer) orin the pixel portion. In this case, electrostatic damage can beprevented by manufacturing the protective circuit according to a similarstep to that of the above-described TFT and by connecting the gatewiring layer of the pixel portion to the drain wiring layer or thesource wiring layer of the diode.

Note that any of Embodiment Modes 1 to 8 can be applied to thisembodiment. In Embodiments 2 and 3, a liquid crystal display panel and alight emitting display panel are described as examples of a displaypanel; however, the present invention is not limited thereto. Thepresent invention can be appropriately applied to an active type displaypanel such as a DMD (Digital Micromirror Device), a PDP (Plasma DisplayPanel), a FED (Field Emission Display), or an electrophoretic displaydevice (electronic paper).

Embodiment 4

A mode of a light emitting element which can be applied to the abovedescribed Embodiments is described with reference to FIGS. 23A to 23F.

FIG. 23A shows an example of a light emitting element whose first pixelelectrode 11 is formed of a light transmitting oxide conductivematerial. The first pixel electrode 11 is formed of an oxide conductivematerial containing silicon oxide with a concentration of 1 atomic % to15 atomic %. A layer including a light emitting material 16 is formedthereover, in which a hole injection layer or hole transport layer 41, alight emitting layer 42, and an electron transport layer or electroninjection layer 43 are stacked. A second pixel electrode 17 is formedwith a first electrode layer 33 containing an alkali metal or analkaline earth metal such as LiF or MgAg and a second electrode layer 34formed of a metal material such as aluminum. A pixel of this structurecan emit light from the first pixel electrode 11 side as indicated by anarrow in FIG. 23A.

FIG. 23B shows an example of a light emitting element which emits lightthrough a second pixel electrode 17. A first pixel electrode 11 isformed with a first electrode layer 35 formed of a metal such asaluminum or titanium or a metal material containing the metal andnitrogen with concentrations of a stoichiometric composition ratio orless and a second electrode layer 32 formed of an oxide conductivematerial containing silicon oxide with a concentration of 1 atomic % to15 atomic %. A layer including a light emitting material 16 is formedthereover, in which a hole injection layer or hole transport layer 41, alight emitting layer 42, and an electron transport layer or electroninjection layer 43 are stacked. The second pixel electrode 17 is formedwith a third electrode layer 33 containing an alkali metal or analkaline earth metal such as LiF or CaF and a fourth electrode layer 34formed of a metal material such as aluminum. Each layer is formed tohave a thickness of 100 nm or less so that the layer can transmit light.Accordingly, light can be emitted through the second pixel electrode 17.

FIG. 23E shows an example of a light emitting element which emits lightfrom both sides, through a first pixel electrode and a second pixelelectrode. A light transmitting conductive film having a high workfunction is used for a first pixel electrode 11. A light transmittingconductive film having a low work function is used for a second pixelelectrode 17. Typically, the first pixel electrode 11 may be formed ofan oxide conductive material containing silicon oxide with aconcentration of 1 atomic % to 15 atomic %, and the second pixelelectrode 17 may be formed of a third electrode layer 33 containing analkali metal or an alkaline earth metal such as LiF or CaF and a fourthelectrode layer 34 formed of a metal material such as aluminum, each ofwhich has a thickness of 100 nm or less.

FIG. 23C shows an example of a light emitting element which emits lightthrough a first pixel electrode 11 and a structure in which a layerincluding a light emitting material 16 is formed by sequentiallystacking an electron transport layer or electron injection layer 43, alight emitting layer 42, and a hole injection layer or hole transportlayer 41. A second pixel electrode 17 is formed, from the side of thelayer including a light emitting material 16, with a second electrodelayer 32 formed of an oxide conductive material containing silicon oxidewith a concentration of 1 atomic % to 15 atomic % and a first electrodelayer 35 formed of a metal such as aluminum or titanium or a metalmaterial containing the metal and nitrogen with a concentration of astoichiometric composition ratio or less. The first pixel electrode 11is formed with a third electrode layer 33 containing an alkali metal oran alkaline earth metal such as LiF or CaF and a fourth electrode layer34 formed of a metal material such as aluminum. Each layer is formed tohave a thickness of 100 nm or less so that the layer can transmit light.Accordingly, light can be emitted through the first pixel electrode 11.

FIG. 23D shows an example of a light emitting element which emits lightthrough a second pixel electrode 17 and a structure in which a layerincluding a light emitting material 16 is formed by sequentiallystacking an electron transport layer or electron injection layer 43, alight emitting layer 42, and a hole injection layer or hole transportlayer 41 over a first pixel electrode 11. The first pixel electrode 11is formed to have a similar structure to that shown in FIG. 23A and tobe thick enough to reflect light emitted from the layer including alight emitting material 16. The second pixel electrode 17 is formed ofan oxide conductive material containing silicon oxide with aconcentration of 1 atomic % to 15 atomic %. In this structure, the holeinjection layer or hole transport layer 41 is formed of inorganic metaloxide (typically, molybdenum oxide or vanadium oxide). Accordingly,oxygen to be introduced in forming the second pixel electrode 17 issupplied and hole injection properties are improved. Thus, drive voltagecan be lowered.

FIG. 23F shows an example of a light emitting element which emits lightfrom both sides, through a first pixel electrode and a second pixelelectrode. A light transmitting conductive film having a low workfunction is used for the first pixel electrode 11. A light transmittingconductive film having a high work function is used for the second pixelelectrode 17. Typically, the first pixel electrode 11 is formed with athird electrode layer 33 containing an alkali metal or an alkaline earthmetal such as LiF or CaF and a fourth electrode layer 34 formed of ametal material such as aluminum, each of which has a thickness of 100 nmor less, and the second pixel electrode 17 may be formed of an oxideconductive material containing silicon oxide with a concentration of 1atomic % to 15 atomic %.

Embodiment 5

An equivalent circuit diagram of a pixel of a light emitting displaypanel described in the above described Embodiment and an operatingmethod thereof are described with reference to FIGS. 24A to 24F. In adisplay device in which a video signal is digital, a method foroperating a light emitting display panel includes a method in which avideo signal inputted to a pixel is regulated by voltage and a method inwhich the video signal is regulated by current. The method in which avideo signal is regulated by voltage includes a method in which voltageapplied to a light emitting element is constant (CVCV) and a method inwhich current applied to a light emitting element is constant (CVCC). Inaddition, the method in which a video signal is regulated by currentincludes a method in which voltage applied to a light emitting elementis constant (CCCV) and a method in which current applied to a lightemitting element is constant (CCCC). In this embodiment, a pixel whichperforms CVCV operation is described with reference to FIGS. 24A and24B. A pixel which performs CVCC operation is described with referenceto FIGS. 24C to 24F.

In pixels shown in FIGS. 24A and 24B, a signal line 3710 and a powersupply line 3711 are arranged in a column direction and a scanning line3714 is arranged in a row direction. In addition, the pixels include aswitching TFT 3701, a driving TFT 3703, a capacitor element 3702, and alight emitting element 3705.

Note that the switching TFT 3701 and the driving TFT 3703 operate in alinear region when they are turned on. The driving TFT 3703 has a roleof controlling voltage application to the light emitting element 3705.It is preferable from the viewpoint of manufacturing steps that both ofthe TFTs have the same conductivity. In this embodiment, the TFTs areformed to be p-channel TFTs. Further, the driving TFT 3703 may be notonly an enhancement mode TFT but also a depletion mode TFT. In addition,a ratio of a channel width W to a channel length L (W/L) of the drivingTFT 3703 preferably ranges from 1 to 1000, although it depends on themobility of the TFT. The higher the W/L is, the more improved electricalcharacteristics of the TFT are.

In the pixels shown in FIGS. 24A and 24B, the switching TFT 3701 is aTFT for controlling input of a video signal to the pixel. When theswitching TFT 3701 is turned on, the video signal is inputted to thepixel. Then, voltage of the video signal is stored in the capacitorelement 3702.

In FIG. 24A, an opposite electrode of the light emitting element 3705 isan anode and an electrode connected to the driving TFT 3703 is acathode, in the case where the power supply line 3711 is Vss and theopposite electrode of the light emitting element 3705 is Vdd, in otherwords, in the case of FIGS. 23C, 23D and 23F (reverse stackedstructure). In this case, luminance variation due to variation incharacteristics of the driving TFT 3703 can be suppressed.

In FIG. 24A, an opposite electrode of the light emitting element 3705 isa cathode and an electrode connected to the driving TFT 3703 is ananode, in the case where the power supply line 3711 is Vdd and theopposite electrode of the light emitting element 3705 is Vss, in otherwords, in the case of FIGS. 23A, 23B and 23E (sequence stackedstructure). In this case, voltage of the video signal is held in thecapacitor element 3702 and the driving TFT 3703 operates in a linearregion by inputting the video signal having higher voltage than Vdd tothe signal line 3710. Therefore, luminance variation due to variation incharacteristics of the TFT can be suppressed.

The pixel shown in FIG. 24B has a similar structure to that of the pixelshown in FIG. 24A except that a TFT 3706 and a scanning line 3715 areadded.

In the TFT 3706, ON or OFF is controlled by the scanning line 3715 thatis arranged anew. When the TFT 3706 is turned ON, an electric chargeheld in the capacitor element 3702 is discharged, and the TFT 3703 isturned OFF. In other words, it is possible to make a state in whichcurrent is forced not to flow through the light emitting element 3705 bydisposing the TFT 3706. Therefore, the TFT 3706 can be referred to as anerasing TFT. Accordingly, in the structure in FIG. 24B, a lightingperiod can be started simultaneously with or immediately after a startof a writing period without waiting for writing of signals in allpixels. Consequently, a duty ratio of light emission can be improved.

In the pixel having the operation structure, the value of electriccurrent of the light emitting element 3705 can be determined by thedriving TFT 3703 which operates in a linear region. According to theabove-described structure, luminance variation of the light emittingelement, which is caused by variation in characteristics of the TFT, canbe suppressed, and a display device with improved image quality can beprovided.

Subsequently, a pixel which performs CVCC operation is described withreference to FIGS. 24C to 24F. The pixel shown in FIG. 24C is providedwith a power supply line 3712 and a current control TFT 3704 in additionto the pixel structure shown in FIG. 24A.

A pixel shown in FIG. 24E is different in the way that a gate electrodeof a driving TFT 3703 is connected to a power supply line 3712 arrangedin a row direction, but other than that, the pixel has a similarstructure to the pixel shown in FIG. 24C. In other words, equivalentcircuit diagrams of both of the pixels shown in FIGS. 24C and 24E arethe same. However, each power supply line is formed using a conductivelayer in a different layer when the power supply line 3712 is arrangedin a column direction (FIG. 24C) and when the power supply line 3712 isarranged in a row direction (FIG. 24E). Here, a wiring connected to thegate electrode of the driving TFT 3703 is focused and the circuits areseparately shown in FIGS. 24C and 24E to show that the wirings areformed in different layers.

Note that the switching TFT 3701 operates in a linear region and thedriving TFT 3703 operates in a saturation region. In addition, thedriving TFT 3703 has a role of controlling the value of current flowingthrough the light emitting element 3705, and the current controlling TFT3704 operates in a saturation region and has a role of controllingsupply of electric current to the light emitting element 3705.

Pixels shown in FIGS. 24D and 24F have the same structure as the pixelsshown in FIGS. 24C and 24E except that an erasing TFT 3706 and ascanning line 3715 are added.

Note that the pixels shown in FIGS. 24A and 24B also can perform CVCCoperation. In the pixels having the operation structures shown in FIGS.24C to 24F, Vdd and Vss can be appropriately changed as in the pixelsshown in FIGS. 24A and 24B, in accordance with a current flowingdirection through the light emitting element.

In the pixel having the above structure, the current controlling TFT3704 operates in a linear region, so that slight variation in Vgs(gate-source voltage) of the current controlling TFT 3704 does notinfluence the value of electric current of the light emitting element3705. In other words, the value of electric current of the lightemitting element 3705 can be determined by the driving TFT 3703 whichoperates in a saturation region. According to the above-describedstructure, luminance variation of the light emitting element, which iscaused by variation in characteristics of the TFT, can be suppressed,and a display device with improved image quality can be provided.

It is preferable to make a semiconductor film of a driving TFT largespecifically in the case of forming a thin film transistor having anamorphous semiconductor or the like, since variation of the TFT can bereduced. Since the pixels shown in FIGS. 24A and 24B have a small numberof TFTs, an aperture ratio can be increased.

The structure in which the capacitor element 3702 is provided is shown;however, the present invention is not limited thereto. When a gatecapacitor or the like can be used as the capacitor that can hold a videosignal, the capacitor element 3702 may not be provided.

When the semiconductor region of the thin film transistor is formed ofan amorphous semiconductor film, a threshold value is easily shifted.Therefore, a circuit which compensates the threshold value is preferablyprovided in the pixel or in the periphery of the pixel.

Such an active matrix light emitting device is considered to beadvantageous, because low voltage driving is possible since each pixelis provided with TFTs when a pixel density is increased. On the otherhand, a passive matrix light emitting device in which TFTs are providedfor every column can also be formed. In the passive matrix lightemitting device, TFTs are not provided for each pixel; therefore, a highaperture ratio can be obtained.

In the display device according to the present invention, a drivingmethod for screen display is not particularly limited. For example, adot-sequential driving method, a line-sequential driving method, aplane-sequential driving method, or the like can be used as the drivingmethod. Typically, the line-sequential driving method is employed, and atime-division gray scale driving method or an area gray scale drivingmethod may be appropriately used. In addition, a video signal inputtedto a source line of the display device may be an analog signal or adigital signal. A driving circuit or the like may be appropriatelydesigned in accordance with the video signal.

As described above, various pixel circuits can be used.

Embodiment 6

Mounting of a driver circuit on the display panel described in theabove-described embodiment is described in Embodiment 6 with referenceto FIGS. 26A to 26C.

As shown in FIG. 26A, a signal line driver circuit 1402 and scanningline driver circuits 1403 a and 1403 b are mounted on the periphery of apixel portion 1401. In FIG. 26A, an IC chip 1405 is mounted on asubstrate 1400 by a known anisotropic conductive adhesive agent, amounting method using an anisotropic conductive film, a COG method, awire bonding method, a reflow treatment using a solder bump, or the likeas the signal line driver circuit 1402, the scanning line drivercircuits 1403 a and 1403 b, and the like. Here, the COG method is used.Then, the IC chip is connected to an external circuit through an FPC(flexible printed circuit) 1406.

As shown in FIG. 26B, in the case of forming a TFT of a SAS or acrystalline semiconductor, a pixel portion 1401, scanning line drivercircuits 1403 a and 1403 b, and the like may be integrated over asubstrate, and a signal line driver circuit 1402 and the like may beseparately mounted as an IC chip. In FIG. 26B, an IC chip 1405 ismounted on a substrate 1400 by a COG method as the signal line drivercircuit 1402. Then, the IC chip is connected to an external circuitthrough an FPC 1406.

Further, as shown in FIG. 26C, a signal line driver circuit 1402 and thelike may be mounted by a TAB method instead of the COG method. Then, anIC chip is connected to an external circuit through an FPC 1406. In FIG.26C, the signal line driver circuit is mounted by a TAB method; however,a scanning line driver circuit may be mounted by the TAB method.

When the IC chip is mounted by the TAB method, the pixel portion can beformed to occupy a large area over the substrate, and thus a frame canbe narrowed.

The IC chip is formed using a silicon wafer, but an IC in which acircuit is formed over a glass substrate (hereinafter referred to as adriver IC) may be provided in place of the IC chip. Since the IC chip istaken out of a circular silicon wafer, there is limitation on the shapeof a mother substrate. On the other hand, the driver IC has a glassmother substrate and there is no limitation on the shape. Thus,productivity can be improved. Therefore, the geometry of the driver ICcan be freely set. For example, when the driver IC is formed to have along side of 15 mm to 80 mm in length, the necessary number of thedriver ICs can be reduced as compared with the case of mounting the ICchip. Accordingly, the number of connection terminals can be reduced andyield in manufacturing can be improved.

The driver IC can be formed using a crystalline semiconductor formedover a substrate, and the crystalline semiconductor may be formed bycontinuous wave laser light irradiation. A semiconductor film formed bycontinuous wave laser light irradiation has few crystal defects and hascrystal grains with large grain diameters. Accordingly, a transistorhaving such a semiconductor film has favorable mobility and responsespeed and thus high-speed drive can be performed, which is suitable forthe driver IC.

Embodiment 7

A display module is described in Embodiment 7. Here, a liquid crystalmodule is described as an example of a display module with reference toFIG. 18.

An active matrix substrate 1601 and an opposite substrate 1602 are fixedto each other with a sealing agent 1600 and a pixel portion 1603 and aliquid crystal layer 1604 are provided therebetween to form a displayregion.

A colored layer 1605 is necessary to perform color display. In the caseof an RGB system, the colored layer corresponding to each color of red,green, and blue is provided corresponding to each pixel. Polarizingplates 1606 and 1607 are provided outside the active matrix substrate1601 and the opposite substrate 1602. In addition, a protective film1616 is formed on the surface of the polarizing plate 1606, whichrelieves impact from outside.

A connection terminal 1608 provided for the active matrix substrate 1601is connected to a wiring substrate 1610 through an FPC 1609. The FPC ora connection wiring is provided with a pixel driver circuit (an IC chip,a driver IC, or the like) 1611, and an external circuit 1612 such as acontrol circuit or a power supply circuit is incorporated in the wiringsubstrate 1610.

A cold cathode fluorescent tube 1613, a reflecting plate 1614, and anoptical film 1615 are a backlight unit and serve as a light source toproject light on a liquid crystal display panel. The liquid crystalpanel, the light source, the wiring substrate, the FPC, and the like areheld and protected by a bezel 1617.

Note that any of Embodiment Modes 1 to 8 can be applied to thisembodiment.

Embodiment 8

An appearance of a light emitting display module is described inEmbodiment 8 as an example of a display module with reference to FIGS.25A and 25B. FIG. 25A is a top view of a panel in which a firstsubstrate and a second substrate are sealed with a first sealing agent1205 and a second sealing agent. FIG. 25B corresponds to across-sectional view taken along a line A-A′ in FIG. 25A.

In FIG. 25A, reference numeral 1201 shown in dashed line denotes asignal line (source line) driver circuit; 1202, a pixel portion; and1203, a scanning line (gate line) driver circuit. In this embodiment,the signal line driver circuit 1201, the pixel portion 1202, and thescanning line driver circuit 1203 are in a region sealed with the firstsealing agent 1205 and the second sealing agent. A high-viscosity epoxyresin including filler is preferably used as the first sealing agent1205. A low-viscosity epoxy resin is preferably used as the secondsealing agent. The first sealing agent 1205 and the second sealing agentare preferably materials which transmit as little water or oxygen aspossible.

A drying agent may be provided between the pixel portion 1202 and thefirst sealing agent 1205. Moreover, in the pixel portion, a drying agentmay be provided over a scanning line or a signal line. It is preferableto use a substance which adsorbs water (H₂O) by chemical adsorption likean oxide of an alkaline earth metal such as calcium oxide (CaO) orbarium oxide (BaO) as the drying agent. However, without being limitedthereto, a substance which adsorbs water by physical adsorption, such aszeolite or silica gel, may also be used.

The drying agent can be fixed to the second substrate 1204 with agranular substance of the drying agent contained in a highly moisturepermeable resin. As the highly moisture permeable resin, an acrylicresin can be used, such as ester acrylate, ether acrylate, esterurethane acrylate, ether urethane acrylate, butadiene urethane acrylate,special urethane acrylate, epoxy acrylate, amino resin acrylate, oracrylic resin acrylate. In addition, an epoxy resin can be used, such asa bisphenol A type liquid resin, a bisphenol A type solid resin, abromine-containing epoxy resin, a bisphenol F type resin, a bisphenol ADtype resin, a phenol resin, a cresol type resin, a novolac resin, acyclic aliphatic epoxy resin, an Epi-Bis type epoxy resin, a glycidylester resin, a glycidyl amine resin, a heterocyclic epoxy resin, or amodified epoxy resin. In addition, another substance may be used. Forexample, an inorganic material such as siloxane polymer, polyimide, PSG(phosphosilicate glass), BPSG (borophosphosilicate glass), or the likemay be used.

The entry of moisture into a display element and the deteriorationcaused thereby can be suppressed without decreasing an aperture ratio byproviding the drying agent in a region overlapped with the scanning lineor by fixing the drying agent to the second substrate with a granularsubstance of the drying agent contained in the highly moisture permeableresin.

Note that reference numeral 1210 denotes a connection wiring fortransmitting a signal to be inputted to the signal line driver circuit1201 and the scanning line driver circuit 1203, and the signal linedriver circuit 1201 and the scanning driver circuit 1203 receive a videosignal or a clock signal from an FPC (flexible printed wiring) 1209 thatis an external input terminal through the connection wiring 1208.

Subsequently, a cross-sectional structure is described with reference toFIG. 25B. A driver circuit and a pixel portion 1202 are formed over afirst substrate 1200 and a plurality of semiconductor elements typifiedby a TFT are included. A signal line driver circuit 1201 as the drivercircuit and a pixel portion are shown. Note that the signal line drivercircuit 1201 is formed using a CMOS circuit which is a combination of ann-channel TFT 1221 and a p-channel TFT 1222.

In this embodiment, TFTs of the signal line driver circuit, the scanningline driver circuit, and the pixel portion are formed over onesubstrate. Therefore, the volume of a light emitting display device canbe reduced.

The pixel portion 1202 has a plurality of pixels each including aswitching TFT 1211, a driving TFT 1212, and a first pixel electrode(anode) 1213 made of a reflective conductive film which is electricallyconnected to the drain of the driving TFT 1212.

An interlayer insulating film 1220 of the TFTs 1211, 1212, 1221, and1222 can be formed of a material containing an inorganic material (suchas silicon oxide, silicon nitride, and silicon oxynitride) or an organicmaterial (such as polyimide, polyamide, polyimide amide,benzocyclobutene, and siloxane polymer) as its main component. When theinterlayer insulating film is formed of siloxane polymer, it becomes aninsulating film having a skeleton structure formed by the bond ofsilicon and oxygen and including hydrogen or/and alkyl group in a sidechain.

An insulator (referred to as a bank, a partition wall, a barrier, amound, or the like) 1214 is formed at both edge portions of the firstpixel electrode (anode) 1213. The insulator 1214 is formed to have acurved surface at an upper edge portion or a lower edge portion thereofin order to increase the coverage of a film to be formed over theinsulator 1214. The insulator 1214 may be formed of a materialcontaining an inorganic material (such as silicon oxide, siliconnitride, and silicon oxynitride) or an organic material (such aspolyimide, polyamide, polyimide amide, benzocyclobutene, and siloxanepolymer) as its main component. The insulator 1214 may be covered with aprotective film (planarizing layer) formed of an aluminum nitride film,an aluminum nitride oxide film, a thin film containing carbon as itsmain component, or a silicon nitride film. Stray light from a lightemitting element to be formed can be absorbed by the insulator 1214 byusing, as the insulator 1214, an organic material in which a materialabsorbing visible light, such as a black pigment or a coloring matter isdissolved or dispersed. Thus, the contrast of each pixel is enhanced.Further, the interlayer insulating film 1220 formed of a light-shieldinginsulator can generate a light-shielding effect when combined with theinsulator 1214.

A layer including a light emitting material 1215 is selectively formedover the first pixel electrode (anode) 1213 by evaporating an organiccompound material.

Thus, a light emitting element 1217 including the first pixel electrode(anode) 1213, the layer including a light emitting material 1215, and asecond pixel electrode (cathode) 1216 is formed. The light emittingelement 1217 emits light to the side of the second substrate 1204.

The light-emitting element 1217 can appropriately have the structuredescribed in Embodiment 5.

A protective stacked layer 1218 is formed to seal the light emittingelement 1217. The protective stacked layer is a stacked layer of a firstinorganic insulating film, a stress relaxation film, and a secondinorganic insulating film. The protective stacked layer 1218 and thesecond substrate 1204 are attached to each other with the first sealingagent 1205 and the second sealing agent 1206. Note that the secondsealing agent is preferably dropped using an apparatus for dropping asealing agent like the apparatus for dropping liquid crystal shown inFIGS. 15A and 15B described in Embodiment 3. After the sealing agent isapplied onto the active matrix substrate by being dropped or dischargedfrom a dispenser, the second substrate is attached to the active matrixsubstrate and ultraviolet curing is performed in vacuo. In this manner,sealing can be performed.

A polarizing plate 1225 is fixed on the surface of the second substrate1204, and a half-wave or quarter-wave retardation plate 1229 and ananti-reflective film 1226 are formed on the surface of the polarizingplate 1225. Alternatively, the half-wave or quarter-wave retardationplates 1229 and the polarizing plate 1225 may be sequentially formedfrom the side of the second substrate 1204. The retardation plate andthe polarizing plate can prevent external light from being reflected bythe pixel electrode. When the first pixel electrode 1213 and the secondpixel electrode 1216 are formed of a light transmitting or semi-lighttransmitting conductive film and the interlayer insulating film 1223 isformed of a material which absorbs visible light or an organic materialin which a material absorbing visible light is dissolved or dispersed,external light is not reflected by each pixel electrode. Therefore, theretardation plate and the polarizing plate may not be used.

A connection wiring 1208 is electrically connected to an FPC 1209 by ananisotropic conductive film or an anisotropic conductive resin 1227.Further, a connection portion of each wiring layer and a connectionterminal is preferably sealed with a sealing resin. This structure canprevent water from a section from entering and deteriorating the lightemitting element.

Note that a space between the second substrate 1204 and the protectivestacked layer 1218 may be filled with an inert gas, for example, anitrogen gas. The entry of water or oxygen can be further prevented.

A colored layer can be provided between the pixel portion 1202 and thepolarizing plate 1225. In this case, full color display can be performedby providing the pixel portion with a light emitting element which canemit white light and by separately providing the second substrate 1204with colored layers showing RGB. In addition, full color display can beperformed by providing the pixel portion with a light emitting elementwhich can emit blue light and by separately providing a color conversionlayer or the like. In addition, each pixel portion can be provided withlight emitting elements which emit red, green, and blue light, and thecolored layer can be used. Such a display module has high color purityof each RBG and can perform high-definition display.

A light emitting display module may be formed using a substrate of afilm, a resin, or the like for either the first substrate 1200 or thesecond substrate 1204 or both thereof. A display device can be reducedin weight, size, and thickness by sealing without using an oppositesubstrate in this manner.

Note that any of Embodiment Modes 1 to 8 can be applied to thisembodiment. A liquid crystal display module and a light emitting displaymodule are described as an example of a display module in thisembodiment; however, the present invention is not limited thereto. Thepresent invention can be appropriately applied to a display module suchas a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), aFED (Field Emission Display), or an electrophoretic display device(electronic paper).

Embodiment 9

Various electronic devices can be manufactured by incorporating thedisplay device described in the above described embodiment into achassis. Examples of electronic devices can be given as follows: atelevision set, a camera such as a video camera or a digital camera, agoggle type display (head mounted display), a navigation system, anaudio reproducing device (a car audio, an audio component, or the like),a personal computer, a game machine, a personal information terminal (amobile computer, a cellular phone, a portable game machine, anelectronic book, or the like), an image reproducing device provided witha recording medium (specifically, a device capable of reproducing arecording medium such as a Digital Versatile Disc (DVD) and having adisplay that can display the image), and the like. Here, a televisionset and a block diagram thereof are shown in FIG. 27 and FIG. 28,respectively and a digital camera is shown in FIGS. 29A and 29B astypical examples of the electronic devices.

FIG. 27 shows a typical structure of a television set that receivesanalog television broadcasting. In FIG. 27, the airwaves for televisionbroadcasting received by an antenna 1101 are inputted to a tuner 1102.The tuner 1102 generates and outputs intermediate frequency (IF) signalsby mixing the high frequency television signals inputted from theantenna 1101 with local repetition frequency signals that are controlledin accordance with the desired reception frequency.

The IF signals taken out by the tuner 1102 are amplified to requiredvoltage by an intermediate frequency amplifier (IF amplifier) 1103.Thereafter, the amplified IF signals are detected by a video detectioncircuit 1104 and an audio detection circuit 1105. The video signalsoutputted from the video detection circuit 1104 are separated intoluminance signals and chrominance signals by a video processing circuit1106. Further, the luminance signals and the chrominance signals aresubjected to the predetermined video signal processing to become videosignals, so that the video signals are outputted to a video outputportion 1108 of the display device of the present invention, typically,a liquid crystal display device, a light emitting display device, a DMD(Digital Micromirror Device), a PDP (Plasma Display Panel), a FED (FieldEmission Display), an electrophoretic display device (electronic paper),or the like. Note that a television using a liquid crystal displaydevice as a display device is a liquid crystal television, and atelevision using a light emitting display device is an EL (ElectroLuminescence) television. The same applies to the case of using anotherdisplay device.

The signals outputted from the audio detection circuit 1105 aresubjected to processing such as FM demodulation by an audio processingcircuit 1107 to become audio signals. The audio signals are thenappropriately amplified to be outputted to an audio output portion 1109of a speaker or the like.

The television set according to the present invention may be applicableto digital broadcastings such as terrestrial digital broadcasting, cabledigital broadcasting, and BS digital broadcasting as well as analogbroadcastings such as terrestrial broadcasting in a VHF band, a UHFband, or the like, cable broadcasting, and BS broadcasting.

FIG. 28 is a front perspective view of the television set, whichincludes a chassis 1151, a display portion 1152, a speaker portion 1153,an operational portion 1154, a video input terminal 1155, and the like.The television set shown in FIG. 28 has the structure as shown in FIG.27.

The display portion 1152 is an example of the video output portion 1108in FIG. 27, which displays images.

The speaker portion 1153 is an example of the audio output portion inFIG. 27, which outputs sound.

The operational portion 1154 is provided with a power source switch, avolume switch, a channel selection switch, a tuning switch, a selectionswitch, and the like to turn ON and OFF the television set, selectimages, control sound, select a tuner, and the like by holding theswitches down. Note that the above-described selection can be carriedout also by a remote-control operation unit, although not shown.

The video input terminal 1155 inputs video signals received fromoutside, e.g., from a VTR, a DVD, a game machine, or the like, to thetelevision set.

In the case where the television set described in this embodiment is awall-mounted television set, a portion for hanging on walls is providedat the rear of the body thereof.

A television set can be manufactured at low cost with high throughputand yield by applying the display device that is one example of asemiconductor device of the present invention to the display portion ofthe television set. Further, a television set can be manufactured at lowcost with high throughput and yield by applying a semiconductor deviceof the present invention to a CPU controlling a video detection circuit,video processing circuit, an audio detection circuit, or an audioprocessing circuit of the television set. Consequently, the televisionset can be used for various intended purposes, in particular, a largearea display medium such as a wall-mounted television set, aninformation display board used in a railway station, airport, or thelike, and an advertisement display board on the street, and the like.

FIGS. 29A and 29B show an example of a digital camera. FIG. 29A is afront perspective view of the digital camera, and FIG. 29B is a rearperspective view thereof. In FIG. 29A, the digital camera includes arelease button 1301, a main switch 1302, a viewfinder window 1303, flash1304, a lens 1305, a lens barrel 1306, and a chassis 1307.

In FIG. 29B, the digital camera also includes a viewfinder eyepiece1311, a monitor 1312, and an operational button 1313.

When the release button 1301 is held halfway down, a focus adjustmentmechanism and an exposure adjustment mechanism are operated.Subsequently, holding the release button all the way down releases ashutter.

The digital camera is turned ON or OFF by pressing or turning the mainswitch 1302.

The viewfinder window 1303 is provided above the lens 1305 on the frontface of the digital camera, and is used to check a shooting range and afocusing point through the viewfinder eyepiece 1311 shown in FIG. 29B.

The flash 1304 is provided at the upper portion of the front face of thedigital camera. In the case of photographing a subject of the lowluminance level, auxiliary light is emitted simultaneously when therelease button is held down and the shutter is opened.

The lens 1305 is provided on the front of the digital camera. The lensincludes a focusing lens, a zoom lens, and the like. A shooting opticalsystem includes the lens along with a shutter and an aperture, which arenot shown in the drawing. An image sensing device such as a CCD (ChargeCoupled Device) is provided at the rear of the lens.

The lens barrel 1306 is used for shifting the lens position to focus thefocusing lens, the zoom lens, and the like on a subject. At the time oftaking a picture, the lens barrel is protruded from the body so that thelens 1305 is shifted toward a subject. At the time of carrying thedigital camera, the lens 1305 is stored inside the main body to becompact. Note that, although the lens barrel can be protruded to take aclose-up picture of a subject in this embodiment, the present inventionis not limited to the structure. The present invention may be applied toa digital camera which can take a close-up picture without protruding alens barrel due to a structure of a shooting optical system inside thechassis 1307.

The viewfinder eyepiece 1311 is provided at the upper portion of therear of the digital camera, through which the shooting range and thefocusing point are checked by sight.

The operational button 1313 is a button for various kinds of functionsand is provided at the rear of the digital camera. The operationalbutton includes a setup button, a menu button, a display button, afunctional button, a selection button, and the like.

A digital camera can be manufactured at low cost with high throughputand yield by applying the display device that is one example ofsemiconductor devices of the present invention to a monitor. Inaddition, a semiconductor device of the present invention is applied toa CPU that conducts a related process according to input operation ofvarious functional buttons, a main switch, a release button and thelike; a circuit that conducts an automatic focusing operation and anautomatic focus adjusting operation; a driving control circuit ofelectronic flash; a timing control circuit that controls driving of aCCD; an imaging circuit generating a video signal from aphotoelectric-converted signal by an image sensing device such as a CCD;an A/D conversion circuit that converts a video signal generated in theimaging circuit to a digital signal; a CPU controlling each circuit suchas a memory interface that writes video data to a memory and reads videodata; and the like, and therefore, a digital camera can be manufacturedat low cost with high throughput and yield.

1. A wiring substrate comprising: a substrate; and a wiring formed overthe substrate; and wherein the wiring comprises a conductive layerformed using first metal particles, wherein an organic resin layer isprovided on a side of the wiring and second metal particles aredispersed in the organic resin layer, wherein the first metal particlesand the second metal particles are formed from a same metal element,wherein size of the first metal particles is larger than size of thesecond metal particles wherein the organic resin layer has a curvedsurface.
 2. The wiring substrate according to claim 1, wherein the metalelement is a plurality of metal elements.
 3. The wiring substrateaccording to claim 1 comprising an insulating layer or a semiconductorlayer that is in contact with the wiring and the organic resin layer. 4.The wiring substrate according to claim 1, wherein a rate of the metalelement in the wiring is higher than that in the organic resin layer. 5.The wiring substrate according to claim 1, wherein the organic resinlayer is provided on both sides of the wiring.
 6. The wiring substrateaccording to claim 1, wherein the wiring is linear.
 7. The wiringsubstrate according to claim 1, wherein a cross-section of the wiring isa quadrilateral having approximate orthogonal angles.
 8. The wiringsubstrate according to claim 1, wherein a cross-section of the wiring isan approximate trapezoid.
 9. The wiring substrate according to claim 1,wherein in a cross-section of the wiring, a width of the wiring that isin contact with the substrate is narrower than a width of a top surfaceof the wiring.
 10. The wiring substrate according to claim 1, wherein ina cross-section of the wiring, a width of the wiring that is in contactwith the substrate is wider than a width of a top surface of the wiring.11. The wiring substrate according to claim 1, wherein in across-section of the wiring, a width of the wiring is 0.3 μm or more and1.0 μm or less.
 12. The wiring substrate according to claim 1, whereinin a cross-section of the wiring, the width of the wiring is 0.5 μm ormore and 0.8 μm or less.
 13. A semiconductor device comprising asemiconductor element including the wiring substrate according to claim1 as a gate electrode.
 14. The semiconductor device according to claim13, wherein the semiconductor element is a thin film transistor.
 15. Thesemiconductor device according to claim 13, wherein the semiconductorelement is an organic semiconductor transistor.
 16. The wiring substratecomprising according to claim 1, wherein the substrate is selected fromthe group of a glass substrate, a quartz substrate, a ceramic substrate,a plastic substrate, a silicon wafer, and a metal plate.
 17. Asemiconductor device comprising: a semiconductor film; and a wiring,wherein the wiring comprises a conductive layer formed using first metalparticles, wherein an organic resin layer is provided on a side of thewiring and second metal particles are dispersed in the organic resinlayer, wherein the first metal particles and the second metal particlesare formed from a same metal element, wherein size of the first metalparticles is larger than size of the second metal particles, wherein theorganic resin layer has a curved surface.